I'm asking myself that question today as R.J. prepares to send Ela out to meet her next foe--a god-king who isn't all that he should be. Or is he? Perhaps. As I'm mentally walking around this villain and contemplating his mortal flaws, I realize that the proper villain can make a novel. Lift it from mundane to extraordinary. Caricature-villains, on the other hand, drag down a plot--often disastrously. Not good.
So, what am I looking for? Complexity. Touches of mortal weakness, even tenderness, that reveal my villain's soul. (Yes, despite our tendency to remove all human characteristics from the most evil beings and separate them from us, villains do have souls.)
Often, when I'm creating villains, I remember a chief baddie from my Children's Picture Bible. I'll never forget turning the pages and finding--gasp!--this startled man being threatened by huge serpents. Eew! My kid-self wanted those snakes out of the picture. NOW.
Later, when I realized Pharaoh lost what he perhaps treasured most, his son and heir, I wondered if the experience changed his hard heart and truly humbled his lamentably proud soul. Was there hope of redemption for this death-wish-arrogant king?
Will there be hope of redemption for R.J.'s overbearing god-king?
Don't ask me. I'm just the bystander.
Anyway, isn't it my job to keep you guessing?