If we're going with my (poorly self-)defined powers, matter manipulation on an atomic scale allows:

Alchemy(Making Gold Worth Less by faking a Midas Touch)
Self-transformation(includes Rapid Healing by fusion)
Transformation of others(as above)
"Teleportation"(actually, the movement of myself via fission/fusion of component molecules)
Big Appetite(being essentially a miniature sun)
Ending World Hunger(by converting the below into food)
Ending Pollution(see above)

There might be more, but as you can see, potential for both. I guess I'd be bi-polar, sometimes a hero, sometimes a villain, depending on my mood.