You know how there are different kinds of villains.

People tend to like those utterly evil ones. Sometimes not explaining why that person is evil makes him so much more appealing.

When you have reasons for your evilness, it just makes them more... human?

Think Sandman, think Doc Ock.

Yes you might also have a softer side for them because you pity them and you know another side of their story.

People also tend to see bad asses whose cause was mental-instablity as weaker. I thought Pirates 3 could have a better ending with the showdown between the 3 ships. It was a total ownage for the pirates and in my personal view, i thought that pulled down the story a little.

But when a true EVIL villain really comes out, people dig them. People love them.

Yet, i can't think of a totally evil Human character right now. They all say that Humans are all born good.