Mewtwo VS Frieza
Who would win? I honestly can't even fathom this fight.
For argument's sake imagine that Frieza has transformed into his perfect form and that he's at 100% of his power level, and that for Mewtwo, he has all his Pokemon clone minions, is LvL 100, knows all the abilities psychic type Pokemon can know, and he has battle items (X speed, X Attack, etc).