Molecule Man

Molecule Man is a supervillain from Marvel comics who, as his name implies, has the startling talent of being able to control reality on a subatomic level: arguably making him one of the most powerful beings in the universe if he put his mind to it.

Molecule Man has also been a reluctant hero at times so his moral standing could be seen as "grey" rather than purely evil/criminal - though he tended to be more of a villain in his earlier appearances: Molecule Man was powerful enough to once move an entire mountain which he tried to use to crush the Avengers, Hulk managed to hold this mountain up however (which has been seen as one of Hulk's greatest shows of strength).