"Oh... it's the Kaio-ken attack. It's like a massive upsurge of energy. Everything is heightened: power, speed, even hearing and vision improve dramatically. You sort of become a super-self. But it can only be sustained for a short time, so you have to get the job done quickly."
Kaio-ken (界王拳 Kaiōken, lit. "Realm King Fist") is a technique invented by King Kai; however, Goku is the only person ever to use it successfully. It is a technique that multiplies the user's ki for a "heartbeat" - thus increasing their power and speed and enabling them to inflict serious damage to opponents who are considerably stronger than them. However, the downside of the Kaio-ken is that it takes a heavy toll on the user's body, making them more vulnerable to enemy attacks. While in the state, the user's aura color becomes crimson. The technique requires the use of ki control to handle it properly.
As a result of the Kaio-ken, the user's base power level, strength, speed, and even sensory awareness greatly increase for an instant. With training, the length of activation can be increased, as shown during Goku's extended use of the technique against Frieza; eventually during the fight with Hit, Goku manages to hold a casual conversation with the technique active, and uses it continuously during their next engagement. This change is quantified as doubling the user's power level for the base Kaio-ken technique. This short burst of power beyond the body's normal maximum output comes at the cost of increasing the flow of Ki within the user's body, taxing it and requiring great skill and concentration to keep under control. The uprise of ki flowing inside could easily obliterate them, and even when kept under proper control still causes intense muscle spasms, pain and weakness after prolonged use. After using the Kaio-ken x4 to overpower Vegeta's Galick Gun, Goku's entire body was thrashed, and he could barely move without hurting himself. Even one friendly slap on the back from a gracious Yajirobe caused Goku to scream out in agony.
Whilst already a useful technique in its base form, the technique's true potential is in its ability for the power multiplier to be stacked, from doubling of the base Kaio-ken to a tripling, quadrupling and even further. The limits of the multiplier appear to be linked to the user's body toughness in addition to experience, so Goku is able to increase his durability and base strength through training and in turn gain an even higher power multiplier from the Kaio-ken. In Dragon Ball Z, when Goku first learned the Kaio-ken, the furthest he could handle was the Kaio-ken x4 (though his body was heavily damaged even after a x3 multiplier). However, through training at 100x gravity and then later with his dramatic strength increase after his fight with Captain Ginyu, he was able to withstand astounding multiplications of the Kaio-ken technique, such as Kaio-ken x10 and Kaio-ken x20 (which is said to be the maximum in the anime). The highest multiplication for the Kaio-ken ever seen was Kaio-ken x20, which Goku used against Frieza.
In Dragon Ball Super, it was mentioned by Old Kai that using Kaio-ken alongside Super Saiyan is almost impossible or rather lethal because the intense emotional turmoil caused by the Super Saiyan transformation would not allow precise ki control to survive the technique. Only a fully controlled and calm Ki could be combined with the Kaio-ken, as it happens with the Super Saiyan Blue.
When using the Kaio-ken, the user gains a red and exploding aura, and in turn, their whole body and clothes acquire a reddish tint. The power of the aura also bristles the user's hair and clothes if they have any. Unlike other transformations (like the Super Saiyan or Golden Frieza), the Kaio-ken must remain with its aura active all the time. If the user is not very used to the technique, it generates great stress to their body, enough to increase the muscle mass and blood pressure (in the form of popped out veins).
Usage and Power
Dragon Ball Z
The first time Goku used the Kaio-ken was during the Saiyan conflict when he used it to catch up with and cripple Nappa before he could kill Gohan and Krillin with his Break Cannon mouth blast. Later, while Goku started to battle Vegeta, he realized he could not defeat Vegeta even with the Kaio-ken; so he powered up to Kaio-ken x3, raising his battle strength to over 24,000 and overpowering Vegeta. To prevent Vegeta from destroying the Earth with his Galick Gun, he used a Kaio-ken x3 Kamehameha, a combination of the Kaio-ken x3 and the Kamehameha, in an attempt to save himself and the Earth, initiating an Energy Clash. When both of their attacks proved unable to overtake the other, Goku used the Kaio-ken x4, surging through Vegeta's Galick Gun and blasting him into the sky.
Goku also used the Kaio-ken briefly when he fought Vegeta's Great Ape form, but was whipped aside by Vegeta's tail, surprised at Vegeta for remaining as agile as ever even in the huge size of the Great Ape transformation. During the Battle on Planet Namek, Goku uses the ability during his fight with Jeice and Burter in order to increase his power up to 300,000 according to Dragon Ball Z: The Anime Adventure Game, so that he could outmatch Burter and Jeice's combined power level of 175,000. Later when Goku fought Captain Ginyu, he demonstrated his Kaio-ken in a prolonged way, increasing his battle strength to a power level around 180,000, thus shocking Ginyu and Jeice. After being healed in the rejuvenation chamber following his attack from Vegeta when Goku himself had switched bodies with Ginyu, Goku battled with Frieza using a Kaio-ken once again.
After realizing Goku was stronger than the others he had battled from Ginyu to Piccolo and even Vegeta, Frieza used 50% of his maximum power, which gave him an enormous power boost. According to Tien Shinhan and King Kai in the manga (as well as the English dub of Dragon Ball Z Kai), Goku was using Kaio-ken x10 throughout the fight, to have even a chance at battling Frieza, but even this was not nearly enough. Goku then attempted to use the Kaio-ken x20, which very briefly gave him speed and power enough to strike Frieza, setting him up for a Kamehameha, which Frieza amazingly held off with one hand before taking the full extent of the blast. Unfortunately, though showing physical signs of being harmed, Frieza was barely hurt by the attack. He did, however, appear shocked by Goku's power, remarking that there was "something strange" about him and wondering how a Saiyan could have such "incredible power". The attack left Frieza feeling somewhat threatened, as he remarks to himself that he "must take him out now!" A short time later, Goku transformed into a Super Saiyan for the first time, which greatly overshadowed the Kaio-ken and gave him the strength to finally overpower Frieza.
Goku's battle against Frieza is the last time the Kaio-ken was used in the original manga, as the introduction of Super Saiyan outclassed it. However, in the anime filler fight against Pikkon at the Other World Tournament, Goku uses a Kaio-ken and Super Saiyan combination (something he calls a "Super Kaio-ken"), which gives him an incredible power increase. Because of this one instance, it appears that Goku can also demonstrate the Kaio-ken's usability in transformed states, which potentially means he can make his transformed forms many times stronger. However, Goku also is very exhausted after using it due to the stress of the Super Saiyan form combined with this technique and cannot perform this technique unless dead. If used alive, he would otherwise be killed using the Super Kaio-ken, so the Kaio-Ken was rendered obsolete for a long time. However, after Goku obtained the Super Saiyan Blue form and its perfect ki control during Dragon Ball Super, this sparked the return of the Kaio-Ken technique; which this time is combined with this powerful and easily controlled Super Saiyan form (see below).
Dragon Ball Super
In the anime, according to Goku, using Kaio-ken alongside the Super Saiyan forms would be too overwhelming on the body, due to the forms using a lot of stamina, and would most likely result in immediate death. However, when Goku obtained the Super Saiyan Blue form, which required perfect innate ki control and a calm mind, utilizing the Kaio-ken technique alongside it became possible. So during his training, Goku began developing a god-like Kaio-ken technique for eventual use against Beerus. He first attempted the technique against Hit during the Tournament of Destroyers, noting that it was incomplete with only a 10% chance of success, meaning Goku needed absolute concentration when activating it, otherwise it would kill him. Goku succeeded in combining the transformation with the Kaio-ken x10, which gave him the ability to effectively counter Hit's improved Time-Skip technique. However, due to the Kaio-ken's risks, Goku could not keep fighting for very long and ended up surrendering the match as his time had run out. After ending the technique, Goku was in extreme pain as he was suffering from extreme muscle contractions. Due to the reckless use of his Ki this way, Goku ended up suffering from Delayed Onset Ki Disorder for some time and caused King Kai to warn him of the danger of using the X10 Super Saiyan Blue Kaio-ken as his body could not handle such reckless ki usage without proper training first and if he continued to do so he ran the risk of never being able to get stronger.
During the Project Zero Mortals, Goku used the Kaio-ken once again in the Super Saiyan Blue form while fighting Fused Zamasu. He did this as a last resort to break Fused Zamasu's Barrier of Light after losing strength in both of his arms and having his left leg crushed. Though he succeeded in knocking Fused Zamasu down with a swift kick from his right leg thanks to the Kaio-ken, Goku was immediately drained of his power afterward and required a Senzu Bean.
Goku used the Super Saiyan Blue Kaio-ken yet again during his fight with Bergamo at the Zeno Expo, after realizing his power to grow stronger and bigger through his punches. He later used it again during his fight with Top.
While sparring with Gohan, his son asked Goku to fight with all of his strength. Goku complied, and Goku fought briefly with Gohan. While Gohan was able to keep up with Goku when he was a Super Saiyan Blue, he was quickly defeated when Goku used Kaio-ken.
By the time of the Tournament of Power, Goku has complete mastery over this state. He is able to use the x20 multiplier usage without any physical strain on his body whatsoever. This allowed him to momentarily go toe-to-toe with a suppressed Jiren, but once the Pride Trooper unleashed more of his power, Goku was soundly beaten. Similar events occurred in the manga, where Goku applied the Kaio-ken's principles to Perfected Super Saiyan Blue in an attempt to break his limits, allowing him to fight Jiren slightly better but at the cost of destroying his body.
Super Dragon Ball Heroes
In Dragon Ball Z: The World's Strongest, he first uses it to deflate the bio-warrior Misokatsun. He uses it again soon after to free himself after being frozen solid by Ebifurya, and then easily takes out both Ebifurya and Kishime with it. He later uses the Kaio-ken x3 to attack Dr. Wheelo's giant robotic body and succeeds in breaking off Wheelo's right arm. The two then engage in a Beam Struggle similar to the one Goku and Vegeta have in the Saiyan Saga, and, just like in that struggle, Goku overpowers Dr. Wheelo's blast by using the Kaio-ken x4.
In Dragon Ball Z: The Tree of Might, Goku first uses the Kaio-ken to avoid getting hit by the Great Ape Gohan but is eventually knocked down by him. Goku later uses the Kaio-ken again to defeat all of Turles' henchmen. After Turles becomes more powerful with the fruit from the Tree of Might, Goku uses the Kaio-ken x10 (Kaio-ken x20 in the Funimation dub) to attack him but is still unable to keep up.
In Dragon Ball Z: Cooler's Revenge, during Goku and Cooler's initial fight, Goku seemingly uses the Kaio-ken (though unnoticeable, as it was in "Bold and Fearless"). After Cooler transforms and becomes far more powerful, Goku uses the Kaio-ken to attack him but has no success. Cooler even flies through Goku's Kaio-ken Kamehameha combo.
In Dragon Ball Z: The Return of Cooler, Goku uses the Kaio-ken early on in his battle with Meta-Cooler, but it again proves far too feeble, forcing Goku to go Super Saiyan soon after. Meta-Cooler even mocks him for using the Kaio-ken instead of using the Super Saiyan form that had defeated Cooler in the past right from the start. This would be the last film where Goku utilizes the Kaio-ken to battle the main villain.
In the extended version of Dragon Ball Z: Battle of Gods, a flashback of Goku fighting Vegeta for the first time shows him using the Kaio-ken.
- Kaio-ken Attack - A rush attack used by Goku while using the Kaio-ken technique, against Vegeta.
- Kaio-ken Finish - A rush attack used by Goku while using the Kaio-ken technique, against Nappa.
- Kaio-ken Kamehameha - A combination of the Kaio-ken technique and the Kamehameha used by Goku.
- Super Kaio-ken - A combination of the Kaio-ken technique and the Super Saiyan transformation that is only possible when one is deceased. However, in some video games, certain characters have demonstrated the ability to utilize the Super Kaio-ken while alive without dying, though their ability to survive is left unexplained.
- Super Saiyan Blue Kaio-ken - A state achieved by Goku that consists of using the Kaio-ken while transformed as a Super Saiyan Blue.
- Super Saiyan 4 Kaio-ken - A state achieved by Xeno Gogeta that consists of using the Kaio-ken while transformed as a Super Saiyan 4.
- Maximum Kaio-ken - A more powerful version of the Kaio-ken used by Goku as a Special Move in his God-like Saiyan, Super Saiyan Blue, and GT Kid Goku (base form) in Dragon Ball Fusions. A single use puts the user in Kaio-ken+ status (the normal Kaio-ken requires the move to be used twice to achieve Kaio-ken+ status).
Video Game Appearances
Goku has used the Kaio-ken technique in many of the Dragon Ball video games, usually as a power-up to increase his abilities or physical strength. He uses it in the Gokuden series, Dragon Ball Z Arcade, Dragon Ball Z: Super Butōden, the Budokai Tenkaichi series, Super Dragon Ball Z, and Dragon Ball Z: Burst Limit. In the Budokai series, the Kaio-ken is counted as a transformation rather than a technique. In Dragon Ball Z: Budokai and Dragon Ball Z: Budokai 2, this attack is dubbed as "King Kai Fist", which is more-or-less an accurate translation.
Kaio-ken appears in the Dragon Ball Z Collectible Card Game, on the card "Red Kaio-Ken Drill".
In Dragon Ball Z: Supersonic Warriors, in Krillin's "What-If" story, after dying of the heart virus, Goku (with Fortuneteller Baba's help) returns to teach the Kaio-Ken and Spirit Bomb techniques to Krillin so he can protect the Earth in Goku's place. Krillin can use these techniques in his level 3 form. Both Goku and Krillin will have their Kaio-ken activated if they are in a team-battle as the last team member standing, and when activated it will drain their HP slowly.
In Jump Super Stars and its sequel Jump Ultimate Stars, the Kaio-ken is used as Goku's Special B/Up Special via his 5 Battle Koma version, where it only is used for that one brief attack, which varies between the games. In the first game, Goku is by default in his Super Saiyan form, making it identical to his Super Kaio-ken attack, and it works as a charge attack in order to reach the full sequence of blows when fully charged. In the sequel, Goku instead is still in normal form in BK5, while his Kaio-ken sequence now involves rapid button taps in order to get the full sequence.
In Dragon Ball Online, which is set in Age 1000, it is said that between the end of the original manga and the start of the game, King Kai taught the Kaio-ken skill to the inhabitants of Earth. This includes Earthlings who since the end of the manga have begun practicing different forms of martial arts and the Namekians who fled to Earth after their planet was destroyed by Mira. The Majin race, who were not taught the technique, managed to learn it through mimicry. As such, the technique is obtainable by all three of the game's playable races.
The skill is learned by every class at level 35. The appearance and effects in the game are similar to how it appears in the anime: activating it engulfs the player in a flaring red aura. The self-buff increases the players' movement speed, allowing them to run faster while traveling the environment, as well as their attack speed, chance of critical strike, and maximum attack power while in combat. During its use, both the player's LP (life) and EP (power) are drained and the skill cannot be deactivated manually, but instead deactivates itself when HP is considerably low. Kaio-ken also has a six-minute cool-down period.
The Kaio-ken technique can be amplified over x20, as never seen in previous uses by Goku in the original series. The only increase that comes with multiplying the Kaio-ken buff is the chance of critical strike; for example, activating it doubles the player's critical strike, and the following multiplication would put the increase at x3. Owing to it being accessible to all races and classes, it can be used to increase the strength of trademark techniques other than the Kamehameha, such as Special Beam Cannon, Wolf Fang Fist, Destructo Disc, and Big Bang Attack.
In Dragon Ball Heroes, the Kaio-ken is counted as a transformation rather than a technique. Vegito: Xeno can utilize the Kaio-ken together with his Super Saiyan form to perform the Super Kaio-ken. He presumably acquires the ability to utilize the Kaio-ken and Super Kaio-ken from Goku: Xeno. In Super Dragon Ball Heroes: World Mission, the Kaio-ken is a Special CAA Ability and is classified as a Transformation. Additionally, there is a Special Kaio-ken Accessory that gives a card equipped with it the Kaio-ken ability. However, the aura is no present for characters that normally can't utilize the Kaio-ken. Equipping it will replace any CAA abilities including other transformations such as Super Saiyan forms, Great Ape/Golden Great Ape or Chronoa's Time Power Unleashed transformation.
Kaio-ken, X3 Kaio-ken, and X20 Kaio-ken can be learned and used by the Future Warrior for all races.
"The higher your Ki when you transform, the greater the power-up! But it'll also become a great burden, so watch out!"
— Dragon Ball Xenoverse 2 Kaio-ken Skill description
In Dragon Ball Xenoverse 2, all Kaio-ken skills have been united into a single Awoken Skill, giving higher levels of Kaio-ken based on how may filled ki bars the user has. While in the Kaio-ken state, the user can revert to their base form by pressing the skill's assigned buttons to deactivate it though only if they are at 20x or their ki is low enough to deactivate the Kaio-ken or x3 Kaio-ken or otherwise, they will activate the next multiplier. When in use the Kaio-ken drains stamina and will put the user into a guard break state if they run out of stamina while using it. Like in Xenoverse, it can be used by the Future Warrior regardless of race.
Unlike the previous game, Krillin and Yamcha can't use Kaio-ken, only Goku and the Future Warrior can use it, however, unused voice data files indicate that it was planned to be used by Super Saiyan 4 Gogeta, Goten, and Goku Black in his playable base form as there are unused voice samples for it hidden within the game's voice data files. It can be obtained by the Future Warrior as a reward in Parallel Quest 08: "Invade Earth". Additionally, the Future Warrior and Goku can use the Kaio-ken Attack and Kaio-ken Kamehameha as separate Super Skills, along with the 4x and x20 version of Kaio-ken Kamehameha as separate Ultimate Skills. The Kaioken has two related Super Souls the first being "Body, don't let me down!" which increases normal attack by a large amount but causes the user's health to drain while the Kaioken or its multipliers are activated. The second is "I've been saving this! Kaioken!" which boosts the amount of ki restored by attacking or being attacked by an extra-large amount, boosts stamina recovery by a medium amount and boosts normal attacks by a medium amount when SSGSS Kaioken or Kaioken is activated. The Future Warrior must rely on the Kaioken and its multipliers to activate this Super Soul while SSGSS Goku uses the SSGSS Kaioken and its multiplier. This Super Soul makes it easier to maintain Kaioken and x3 Kaioken due to is stamina recovery boost slowing down the stamina drain though the slow down effect lessens the higher the multiplier.
In Dragon Ball Fusions, Goku uses a variation on the Kaiō-ken, called Max Kaioken (最大界王拳 Saidai Kaiōken, lit. "Maximum Realm King Fist") in his Goku (Super), Super Saiyan Blue, and base GT Goku playable forms. While Super Saiyan 4 Goku appears to be using it in trailers for Dragon Ball Fusions, he is actually using Maximum Charge and it should be noted that Max Kaioken does not appear as part of SSJ4 Goku's learnable Special Moveset (GT Goku and Super Saiyan 4 Goku appear as separate playable characters in Dragon Ball Fusions). However, Super Saiyan 4 KFGoku can utilize Kaioken or Max Kaioken through Freeform Fusion with a Kaioken or Max Kaioken user. Max Kaioken can also be used by several other minor playable characters as well such as the Demon Realm race Offworlder Halto and Namekian Uzma (Lv. 99).
The standard Kaioken also appears as a Special Move that can be learned by certain characters. It can be learned by the Namekian Uzma after reaching Lv. 51. The Ancient Saiyan Skwash can learn both the Kaioken/Max Kaioken and Super Saiyan Special Moves the effects of which can be stacked allowing Skwash to utilize the Super Kaioken (without injury or death). EX-Fusion Tekka and Skwash's EX-Fusions can also utilize Super Kaioken through stacking Super Saiyan (SS) and either Kaioken or Kaioken+.
In Dragon Ball FighterZ, Super Saiyan Blue Goku and the DLC Base Goku can use Kaioken as part of their supers. Super Saiyan Blue Kaioken is SSGSS Goku's Meteor move and leads to an extended beatdown ending in a 10x God Kamehameha. With an extra 2 super stocks, Goku can then follow it up with a Penetrate!-style finisher. Base Goku's Kaioken is a super that requires more player input, with different buttons resulting in different attacks. However, each attack must hit in order for the super to be able to transition into the Kaioken Finisher, otherwise if any miss, the move ends prematurely. If the Kaioken Finisher defeats Goku's current opponent, he will briefly hold them one-handed overhead similar to how he defeated Nappa. Depending on how many teammates Goku has left, the Kaioken Finisher will instead be swapped out for the Kaioken Kamehameha. If Goku has one teammate left, it will be a x3 Kamehameha, while if both of his allies are down, Goku will instead fire a massive x20 Kaioken Kamehameha similar to the one he used against Frieza.
In Jump Force, Goku can utilize Kaio-ken as part of his Meteor Combination rush ability when in his base form or Super Saiyan Blue form Full Awakening (the Kaio-ken is absent when the ability is used while in his Super Saiyan form Awakening and the attack differs slightly). The player's avatar can also utilize the Kaio-ken by using the Meteor Combination ability.
In Dragon Ball Z: Kakarot, Kaioken is treated as a transformation used by Goku. It is the first transformation he acquires. While activated the Kaioken boosts his stats though his HP drains while it is active. However, certain items that grant health regeneration can help counter the HP drain. If the Kaioken is used during Super Saiyan Goku's fight with Frieza on Namek, he will revert to base with the Kaioken activated though he will return to his Super Saiyan form if the Kaioken is deactivated. Interestingly, during the fight with Frieza the Super Saiyan transformation is permanently active when the Kaioken is not in use and is not set in any of the transformation slots (Kaioken is only accessible if it has been assigned to the transformation slot. The Kaioken cannot be stacked on top of the actual Super Saiyan form thus no Super Kaioken.
- The name of the technique has usually been pronounced incorrectly in the English dubs of the anime and video games ("KAY-o-ken", rather than "KAI/KY-o-ken") despite being named after the correctly pronounced King Kai. However, Peter Kelamis (Goku's second voice actor in the Ocean dub of Dragon Ball Z) pronounces it properly in the Ocean dub of The World's Strongest and The Tree of Might, and Sean Schemmel (Goku's adult voice actor in the Funimation dub of the whole franchise) pronounces it correctly in Dragon Ball Z: Burst Limit and in most subsequent games that have been released. The Kaio-ken is also pronounced correctly in the Funimation dub of both Dragon Ball Z Kai and Dragon Ball Super.
- In Xenoverse 2, if Male Voice Option 8 (which is actually the voice of Curtis Arnott/Takahata101, the voice of TeamFourStar's Nappa from Dragon Ball Z: Abridged) is selected for the Future Warrior, then they will shout "KAY-o-ken" when performing the Kaioken Assault Super Skill, though its mispronunciation is done on purpose as an in-joke reference to the common mispronunciation of Kaio-ken in various dubs.
- The only time Goku shouts "Kaio-ken times two" was briefly during the battle with Vegeta, in order to dodge an incoming energy blast. As previously mentioned, there appears to be no actual difference between the Kaio-ken and 2x Kaio-ken. According to the Daizenshuu, Goku's base power level at the time was 8,000, and Vegeta's was 18,000; Goku then powered up to 16,000 with the 2x Kaio-ken, and then 24,000 with the 3x Kaio-ken. If there was a difference between the Kaio-ken and 2x Kaio-ken, then Goku should not have needed to use the 3x Kaio-ken in order to overpower Vegeta.
- In an episode of the original Saban dub, Goku shouts "Kaio-ken times ten" and then "Kaio-ken times twenty" as he fires two Kamehameha blasts toward a comet that his spaceship almost collides with.
- In episodes of both Dragon Ball Z and Dragon Ball Super, Chi-Chi uses a technique similar to Kaio-ken when she gets very angry (though this is just meant for comic relief).
- The website for Dragon Ball Z: Battle of Gods states that "King Kai teaches Goku the "Kaio-ken" and how to gather energy from the planet into one great fighting energy ball. Later King Kai takes on the training of Yamcha, Tien, Chiaotzu, and Piccolo using the same techniques that were successful with Goku." It is unknown whether this statement refers to teaching the Z Fighters the Kaio-ken and Spirit Bomb techniques, or if it is referring to King Kai's training techniques.
- However, Yamcha does use the technique in Xenoverse as does Krillin (who trained under King Kai briefly after his death during the Fusion Saga in the anime before he was resurrected by Porunga). Krillin also learns the technique from Goku in his what-if saga in Supersonic Warriors. It should be noted that Krillin being able to use the technique is likely attributed to his skill when it comes to ki control. However, neither Tien, Chiaotzu, or Piccolo have ever been shown using the technique in any media.
- Technically, Cell could use the Kaio-ken as well, due to having Goku's cells. However, this is not confirmed or shown in the anime or manga (though Cell does claim this in the Funimation dub of Dragon Ball Z Kai).
- In Xenoverse, if the Future Warrior uses the 3x Kaio-ken with Male Voice Option 8 (also voiced by Chris Arnott/Takahata101 from Dragon Ball Z: Abridged), he refers to it as Kaio-ken 3.0.
- Unused voice lines in Xenoverse 2 indicate that Gogeta can use the Kaio-ken as a Super Saiyan 4, and Goten can also use the Kaio-ken (regular, Kaio-ken x3 and Kaio-ken x20).
- Additionally, there are also unused voice lines for Goku Black indicating that he can use the Kaio-ken in his base form. This is ironic given the fact that Black is the former North Kai of Universe 10 and the Kaio-ken is a technique invented by the North Kai of Universe 7 who himself is unable to use it despite being its inventor. This would also make Black the only known Kai (former or current) capable of using a technique which ironically fits with its name's literal translation Realm King Fist. Black can utilize the Spirit Bomb in Super Dragon Ball Heroes another technique invented by the North Kai of Universe 7 that he is unable to use himself making Black the only Kai capable of using both of King Kai's signature techniques.
- Dragon Ball Z: Supersonic Warriors, 2004
- Dragon Ball Xenoverse, 2015
- Dragon Ball Xenoverse 2, 2016
- Dragon Ball Xenoverse 2: Goku Black & Hit English Voice Quotes. youtube (October 28, 2016).
- Dragon Ball Fusions, 2016
- Dragon Ball chapter 229, "The Decisive Battle at Last!" (Page 01, Panel 01)
- Weekly Shōnen Jump #12, 1991
- While not visually shown, the Kaio-ken sound effect plays as Goku attacks Cooler
- XV2 unused voice lines. youtube (July 15, 2017).
- XV2 unused voice lines2. youtube (July 15, 2017).