Evil is difficult to define however, those that are viewed as evil often are not. Since this is a myth forum I might as well say that the clearest defenition I can think of is "Not to conquer but to destroy". Purposeless wrongdoing, even Hitler had a reason for his actions. I don;t believe that there are evil people. Evil is to describe actions not things, rape, murder etc. are evil actions. A person can be very very bad becuase they do evil things, but I don;t think anyone is truly evil, Hitler re-enlivened the German Economy, was a person who worked tirelessly for his people, except he was a psycho, started a war, killed millions of people and in the end commited suicide.
As I said I suppose Evil is a adverb rather than a adjective, and all real people have some flicker of good within them, a reason why they do evil things, though many are misguided and the reason they do it is not a good reason.
-zeph