Full-screen attacks

Giga Attack is a full-screen attack that damages or destroys all enemies. It requires a full gauge, and usually the best way to charge up the energy is by deliberately taking damage. It first appeared in Mega Man X2 as the ability of the Giga Armor's body part, and appeared in all subsequent games after X3; however, some later incarnations do not actually affect the whole screen.

The Giga Attack is not limited to X, however. Zero can also use his own versions of the Giga Attack, as Command Arts learned from defeated Bosses from X4 onwards (the spinoff Mega Man Xtreme 2 also counted). His versions of the attack more closely resembles the original incarnations performed by some of X's armors.

Mega Man Xtreme2

 * X: The Giga Attack from Mega Man X2 was also used here.
 * Zero:

Mega Man X4

 * X: The Force Armor and the Ultimate Armor (both introduced in this game) can perform the powerful Nova Strike. Although classified as a Giga Attack, it's the first in the series not to be a full-screen attack.
 * Zero:

Mega Man X5

 * X: Unlike the two armors from the previous game, the Falcon Armor's Giga Attack closely resembles the original. The Gaea Armor, however, stands out as having the shortest range for a Giga Attack in the entire series.
 * Zero:

Mega Man X6

 * X: Both Giga Attacks of the Blade and Shadow Armors have limited range, since both involve the use of the Z-saber.
 * Zero:

Mega Man X7

 * X: The Glide Armor possesses a similar full-screen attack like that of the Giga and Falcon Armors, renamed the Giga Crush.
 * Zero:

Mega Man X8

 * X: For the first time, a Giga Ability is present, instead of a Giga Attack. The ability, called the X-Drive, increases X's capabilities for a short period of time, which is the case for the Hermes Armor. The Icarus Armor, however, has the same traditional Giga Attack. However, unlike previous Giga Attacks, the attack can be used as long as there is WE. However, the lower the WE, the lower the damage the attack inflicts.
 * Zero:

Other Appearances

 * Omega Zero, the final boss of Mega Man Zero 3, uses weaker variations of Zero's Rakuhouha and Rekkoha.
 * In the commercial for the first Rockman Zero game, Zero was shown creating a powerful explosion after being awakened. The explosion destroyed all enemies, leaving Zero standing strong, which might be a reference to a Giga Attack.
 * Mega Man Model A uses a Giga Crush as its special ability.

Trivia

 * Although Axl doesn't receive a Giga Attack/Ability, some of the attacks he can use while transforming into a Command Mission Boss (e.g. Silver Horn)can hit all enemies.
 * Ironically, the unofficial tribute to Axl, the Model A Biometal, has a Giga Attack, marking the chronological return of the attack to a playable character since Mega Man X8.