Mugetsu

Mugetsu is 's Final Smash in Super Smash Flash 2.

Overview
When performed, a cutscene plays in which Ichigo holds Zangetsu out says, "", and becomes Getsuga. He creates a blade of black Reiatsu in his hand and lifts it, cutting off the music and saying, "", before he swings it down and the cutscene ends. When used on the ground, this will create tall dark veils of Reiatsu on the ground that each deal 30% damage and strong knockback to opponents hit. When used in midair, or when the dark veils reach a ledge, this will instead create a large black crescent-shaped projectile similar to a Getsuga Tenshō that slowly travels forward. Opponents hit by this projectile are dealt 40% damage with incredible knockback. Both the dark veils and the projectile are able to one-hit KO under many circumstances.

Shortly after swinging his sword, Ichigo will revert to his regular form and briefly fall to the ground in pain as the music returns (restarting from the beginning), ending the move.

Origin
Mugetsu is a technique Ichigo uses in  in conjunction with Saigo no Getsuga Tenshō, a technique in which Ichigo becomes the Getsuga itself. Once transformed, Ichigo can use Mugetsu by generating and then swinging a blade of deep black Reiatsu toward his opponent, which causes a massive veil of black Reiatsu to erupt upwards towards them, heavily damaging them. This also envelops them so that even sound cannot be heard during this technique, which is referenced in SSF2 by how the music stops playing upon its use. Afterwards, the Reiatsu continues to rise before finally dissipating.

Mugetsu is one of the most powerful techniques to be used in Bleach. However, shortly after using it, Ichigo loses all of his Shinigami powers and feels intense pain. Because of this, Ichigo has only been able to use it once, which he did against Sōsuke Aizen in chapter 421, DEICIDE23, of the manga Bleach, and subsequently episode 309, "Fierce Fighting Conclusion! Release, the Final Getsuga Tenshō!", of the anime.

Trivia

 * Prior to Beta 1.2, Ichigo's Final Smash was instead a Transformation Final Smash called Bankai Ichigo.
 * The crescent-shaped projectile in Mugetsu shares many attributes to Bankai Ichigo's original neutral special move, Kuroi Getsuga.
 * Prior to Beta 1.3.1, no cutscene played, with Ichigo's actions all being done in-game. This was changed possibly due to the long startup making the Final Smash difficult to land, as opponents had much more time to prepare for and dodge the attack.