All Clear is an explosive arching blade-like energy wave used by Cell in his Perfect form.
First, Cell raises his left hand in the air and charges his energy enough to completely shroud the hand. Cell then fires the attack by turning in a complete circle while swinging his hand, creating many powerful explosions to his surroundings and inflicting a huge amount of damage.
Cell uses this attack to destroy an attacking fleet of the Earth's Military during their assault on the Bio-Android during the 10-day wait before the Cell Games. Commenting that the military might destroy his ring, Cell proceeds to fly towards a nearby mountain to prepare for the military's attack. Despite the military's efforts with nearly endless firings of grenades, rocket launchers, and tanks, Cell emerges from the assault completely unscathed, but the mountain he was standing on was destroyed. While the frantic military prepared to evacuate the area, Cell, with a smirk on his face, fires the attack, destroying the vicinity and completely annihilating every military soldier and vehicle in the area, much to the shock of the world's population and the anger of the Dragon Team, overhearing the situation on the radio.
Video Game Appearance
In Super Dragon Ball Z, Cell uses this technique to destroy the army as he does in the main series.
It is called Punishment Storm in Dragon Ball Z: Battle of Z, where it appears as a physical attack.
All Clear was named in Dragon Ball Xenoverse and appears as one of Perfect Cell's Super Skills. Interestingly, the technique is classified as a Rush Strike rather than an ki attack. In the game, it has the ability to nullify weak ki blasts and can even be used while the user is guarding. It can be learned by the Future Warrior during Cell's training as the Warrior's Master.
"This technique can also be used while guarding. Your character is invulnerable for the duration of the technique if it is performed while guarding against an opponent's attack."
In Xenoverse 2, it returns under the name All Clear as one of Perfect Cell's Super Skills. It can also be learned by the Future Warrior by completing Cell's Initiation Test to train under him. If used while guarding, the user is invulnerable for the duration of the technique.
In Jump Force, the technique appears under the name Perfect Flash.