Y don't you have a look?
Mewtwo arrives on Aeos Island alongside the return of Mega Evolution, which debuted in the Pokémon X and Pokémon Y games. In a unique twist, Mewtwo will have two different Unite licenses—Unite License X: Mewtwo and Unite License Y: Mewtwo.
Both Mega Evolutions use basic attacks as the cornerstone of their battle strategies, with Mega Mewtwo X focusing on melee attacks in a one-on-one setting and Mega Mewtwo Y focusing on ranged attacks and mobility.
Mewtwo can fill its Mega gauge by using basic attacks and moves. Once the gauge is full, Mewtwo will Mega Evolve, which changes its basic attacks and increases its stats for a set time before it changes back to Mewtwo. Expect to Mega Evolve several times per match!