What Makes A Good Villain
I hate serial killers, and not just because they murder people indiscriminately--though that's bad. I hate them because I don't find them interesting. Uniformly, they have a vaguely disturbed childhood or mental illness that spurs them on a bloody spree. They are as much victims of circumstance, in some ways, as their actual victims; just as unable to control their evil fate.
The best villains, in my opinion, have more varied motives. They kill one person because a combination of threats to their livelihood, sense of self, or personal safety made them act violently. Then, they kill more people to cover up the initial killing.
That's what made Walter White in Breaking Bad such a great villain. His back was against the wall and he made an immoral choice that promised easy money. Then, he made another and another until he was Scarface with chemicals instead of coke.