A story can be said to be as strong as it’s antagonist. And they can be said to be the most fun to work with, simply because they do things that to many of them would be unforgivable.
And to me, I always intend to create them with caution and nuance. And to me, here are some defining traits about them.
A villain must have motivations pertaining to who they are, and a reason why they do things. Otherwise, it just make all the evil stuff they do look meaningless.
And a personal reason would be a great one, a belief would add on a lot more. To me, the best villains are the ones which convince me that they were valid in what they sought. And that needs a motivation initially, otherwise it all just fall flat if they do it for nebulous reasons.
A will to force. Motivation isn’t enough. Without Will, you simply have say a normal person. He blames and blames, but he would never take any action. He may be unlikeable, but he isn’t villainous because he simply doesn’t do anything about his personal feelings or convictions.
A villain on the other hand is someone who does things, simply because it is how he sees, and he wants to leave a mark. He wants to let it be known. If he does not have the will, to take action and reap the consequences. Then he is simply the man above, one who does nothing.
The will to do what they do is also another integral part of the villain. Thinking horrible thoughts and enacting them are different things. And so, the will and the drive to do them is another part.
It is also the same thing which separates a hero and a villain and distinguishes them from normal people.
#3 Redeemable Traits
The last thing, a good villain is one that at least seems as though they are redeemable. One that has good traits and bad. One that makes them seem as though they are human.
Every person has both good and bad. And for a villain, it has to be there even as it needs to be tilted to the direction where they have much more faults and strengths.