Well, nobody wakes up in the morning and goes "wow, I think I'm going to be really evil today" unless they are insane. Hence the reasoning behind the saying "the road to hell is paved with good intentions". Hitler and his followers for example believed they were doing the right thing, for the right reasons.
That said, IRL I'm not sure what I'd do with powers since I'd have to be very careful before deciding to do anything. It would give me a differant perspective. Internet rants about what to do are one thing, trying to force those changes single handedly just because I have enough power to try... well that becomes something else entirely for a lot of reasons I won't go into.
That said I'd imagine I'd become a villain by trying to accomplish anything of major import, simply because when you operate on a big scale lots of people are going to dislike what you do no matter what it is. This is one of the reasons why most comic book heroes wind up defending the status/international quo as opposed to trying to upset it for whatever reason. Exceptions like "The Authority" are a *fairly* recent development.
Let's say I ignored social issues entirely feeling that they were for the people themselves to sort out, no matter what I thought, but decided to say use my super abillities to speed up the unification of the world under American principles, the development of space technology, and similar things. Many people might agree with me, but since the use of personal power amounts to force about the time I destroyed a couple of closed cultures, and started whacking world leaders I didn't agree with, I'd be seen as a villain by at least as many people as saw me as a hero.
The fact that I understand that would be one of the reasons why I'd have to be VERY careful in deciding what to do.
Basically I'd imagine the fastest way to become a villain would be to try and become a hero. I mean stop and think about it sometime... back during like the 1970s and 1980s do you think the Russians in those works saw Captain America as a HERO or a VILLAIN? ... and there were a lot of them. Ditto for back when we still had a REAL Superman and noone was ashamed to say he fought for truth, justice, and the American way. Think of it as a population breakdown and it becomes questionable as to whether patrotic heroes had more people thinking of them as heroes or villains at the time period when you consider the other side.
It would be wrong if I had powers to more or less do nothing with them, I mean if they are there, then obviously they are intended to be used... but deciding the right things to do, well... nothing I tried, and no matter whom I teamed up with/worked for, a lot of ordinary people would wind up disliking me simply because any use of powers basically amounts to me using personal might to do what *I* think is right irregardless of the desires of others.