In my theoretical views, I think villains exist in nature because GOD wants to balance the 'ecosystem'. Have you or we ever wondered, what if, all people are good and there aren't any villains? Could it be balanced??
Another view of mine is that, villains exist because of the nature they live in. The environment to be frank. Mostly, people do bad because they love to as they could see the risk of the consequences. Like, oh what will I have to suffer if I steal my friend's charm bracelet? Maybe I could end up in jail. Or maybe she would not be my friend for the rest of my life. But, if we do good, the consequences can easily be detected. Because we have been learnt since infancy, that good deeds deserve good payments while do bad get bad things.
Peer pressure could make it possible in creating villains too. Dealing with the numerous behaviors and pressure from friends could be hard. Feeling isolated and estranged make people into villains either. Not being accepted by peers because of bad look, no talents could be harsh, and these are the main factors nowadays contributing to the increasing in the population of villains.
So for not being or creating a villain, we just have to avoid peer pressure. Be what we really are and always remember that we get shame if we do bad things...so why need shame?? hahahha:D