Who would win in a fight Superman or Mewtwo?

It depends on which incarnation of Superman and Mewtwo one is referring to for their abilities and strengths differ tremendously upon fictitious reality they are inhabit. For example the Silver Age incarnation of superman is capable of traversing the universe at faster than light speeds, withstanding a point blank explosion of a nuclear weapons, and possess an intellect surpassing every area of human psychology. The most impressive display of Mewtwo's power, in any media, could be observed in Pokemon: the first movie- in which Mewtwo psychicly created a hurricane capable of destroying all sentient life on Earth. Mewtwo's ease at creating such a feat raises the question of the true depth of Mewtwo's psychic abilities. The original Golden Age Superman was little more than a tremendously powerful man- a super man if you will (get it?) This superman could not fly though he could leap great distances in a singly bound. At top speed he was slightly faster than a speeding locomotive -superman was was immune to small arms though anything more powerful than that could put him in peril. Video game Mewtwo could be disposed with a few powerful blasts of water or lighting. Superman's most powerfully form could only be defeated by only a few entities in all of Geekdom. While Mewtwo-being exceedingly powerful- really could not compete with Superman's near insurmountable abilities. Least powerful versions of them respectively would be a toss up.