I personally take a different stance. I think the more motivation a villain has, the more sympathetic character they become and the less truly evil they are, but rather ambitious or sometimes victims of the environment. Somebody like Nene from Blue Dragon does what he does just because it gives pleasure. That's really the depth of evil right there. It would be like committing genocide not because humans were mean to you or you had some weird beliefs, but because you simply wanted to. To me that's much more evil.

That makes them paper thin and the storytelling crappy, but that's really not the opinion I'm giving.