"The Great Genki-Dama" (孫悟空最後の決断 Son Gokū Saigo no Ketsudan, lit. "Son Goku's Final Decision") is the one hundred twentieth chapter of Dragon Ball Z and the three hundred fourteenth overall chapter of the Dragon Ball manga.
After his Kamehameha while using Kaio-ken x20 has almost no effect on Frieza, Goku realizes that the tyrant has not been bluffing about his power. Meanwhile, Bulma wonders what is happening and urges Goku to beat Frieza. Krillin wonders how a being as powerful as Frieza can exist, while Piccolo agrees with King Kai's claim that they should have never fought with Frieza. However, Frieza himself is caught off guard as well, wondering where Goku got so much power. He descends to the ground to face Goku, and tells him that his blast hurt.
Enraged that a Saiyan could actually hurt him, Frieza charges at Goku. He successfully headbutts Goku, sending him flying backwards. As Goku gets back onto his knees, Frieza kicks him twice, sending him flying backwards again. As Goku struggles to get up, Frieza asks if he has lost his strength. Goku thinks to himself that he has, and Frieza says that he must want to die at this point. Frieza then attacks Goku by swiping his hand to produce a ki slash which produces a storm of razor sharp ki blast though Goku manages to guard himself from most of the attack, which leaves a large crescent shaped crater in its wake. Gohan prepares to jump into the fight, but Piccolo tells him to wait, as Goku is doing something.
Goku has raised both hands to the sky, which Krillin recognizes as part of the Spirit Bomb technique, which he then explains to Piccolo. Piccolo says that King Kai never mentioned it to him. Gohan wonders if the Spirit Bomb will work on a planet with as little life as Namek. Goku calls for help from life on nearby planets to make the bomb larger. Although worried that the bomb may destroy the planet, he realizes that the entire universe is in danger if he does not stop Frieza. Gohan, Krillin, and Piccolo see the Spirit Bomb beginning to form up in the air above.