Mewtwo Mega Evolves into Mega Mewtwo Y and throws forward a large energy sphere which can trap multiple opponents. Those hit by the sphere are held still and receive a mental shock, which deals 48% (or 35% via the Final Smash Meter) and massive knockback. It can KO Mario from the center of Final Destination at 49%. Aside from the Super Star, Psystrike also ignores any other forms of invincibility.
Mega Mewtwo Y is one of Mewtwo's two possible Mega Evolutions, which is achievable when it is holding a Mewtwonite Y. Unlike most Mega Evolutions (including Mega Mewtwo X), Mega Mewtwo Y is smaller than its normal form instead of being on par or larger than its normal form. Although this is reflected in Mega Mewtwo Y's Defense statistic noticeably decreasing, the remainder of its stats gain tremendous increases.
Although the Mewtwo in the Super Smash Bros. series is primarily based on the Mewtwo from the first Pokémon movie, Mega Mewtwo Y debuted as an alternate form for a different Mewtwo from the sixteenth movie.
Psystrike is Mewtwo's signature move; it debuted in Generation V, and can be learned at level 100 or via Move Relearner. Due to essentially being a more powerful version of Psyshock, Psystrike uses the target's physical Defense stat when calculating damage in spite of being a special category move.
Mewtwo's Final Smash starts as Mewtwo Mega Evolves into Mega Mewtwo Y. It then fires a huge psychic projectile that penetrates enemies and obstacles. This projectile doesn't do any damage, but it freezes every foe it hits in place. They can even be frozen midjump! Afterward, every foe hit with the projectile will take a powerful psychic hit to the head.