Let's start with reasons for them to do their deeds. This is a further detailed version of the back story, and motivations.
Jealousy: The villain, at some point in their life was jealous of another character and vowed to be better then them.
Poverty: The character grew up in poverty, and felt weak their whole life, thus now they want power.
The list of course goes on Pride, Hatred,Revenge,and possibly the biggest good intentions. Which brings me to my next point.
There are two types of goals a villain can have
Good Intentions: The villain is doing his acts of evil for a greater purpose, to better some aspect of life. These people want peace, to some extent and believe that sacrifices must be made in order to get such peace.
Self Interest: These villains do what they do for selfish reasons. It could be hatred or lust for power, but these people usually only care about themselves and don't care how the world turns out.
So pick one of those two options and pick a reason for the said intention. Example a person that acts of Jealousy is a villain of self interest. A villain that acts out of revenge is most likely a villain of good intentions. If you tweak the story you could probably come up with more unique options.
For instance someone that acts out of pride, is assumed to be a villain of self-interest, but if you can connect it to a villain of good intentions, then you'll have a unique villain.
For Example- A person proud of their heritage is sick of how is people are demeaned. So he acts to boost peoples respect for his heritage by forceful means.
Mix in match all these models I have provided and you will make a very convincing villain.
Now I want to talk about things to avoid
Overpowering- Just like you don't want a overpowered hero, the villain must not be overpowered either. Because this will lead to convenience when the hero and villain meet in final battle. "Oh you have all these powers, well I fond this unbeatable wand so there," or " Oh, all of you have abilities, well I'll just block your abilities with a magical bubble that I can extend at will."
Monologuing: This is where the villain has captured the hero and boasts about his plan. This died with The old batman TV show. Yeah "Holy bad writing Batman."
Complete evil- No one is completely evil, unless they are a demon or something. But humans aren't completely evil. All have some good quality or love something. I suppose you could right a sociopath, but that could get boring. A conflicted villain is much more interesting the a one note villain. "I am evil, look I wear black."
So avoid these common mistakes you should be good.
May be a part 3
