Mewtwo

Mewtwo is one of the fastest Pokemon in the Ubers metagame, with a practically unmatched base 130 Speed. It also possesses a Special Attack stat that even surpasses Kyogre, a movepool that covers almost every scenario, and the bulk to back it all up. Mewtwo's movepool is vast enough that it leaves the opponent always guessing what moveset it's running, with even physical sets also being an option. However, its Psychic typing leaves it susceptible to some of the metagame's biggest threats in Snorlax and Deoxys-A, which check it defensively and offensively, respectively. Moreover, Mewtwo often struggles to fit everything it wants in just four moves. While its potential is practically limitless, its sets are usually telegraphed based on just the item revealed. However, mind games can still be played with the opponent up until the final move is revealed.