Most people don't realize it (because it's hard for most to put themselves in someone else's shoes) but if you actually had powers that put you above other people, it would take a great deal of self-control to not start thinking of people as less than you.
It's cliche, but the line used in many movies/anime that goes along the lines of "Are you concerned when you crush an insect? Why should I be concerned with a few worthless humans" isn't too far off. It would be easy to start thinking "Well everyone would be better off if this pest wasn't around" and just start offing people. Hell, think of how many people (who shouldn't think they're above anyone else since we're all human) say that the world would be better off if we just wiped the Middle East off the map (even though there are plenty of innocent people there).
But I suppose that's a bit off topic.