Villains with two heads or gaping sores are pretty easy to spot as the bad guys. But villains who occupy some of the most nerve-jarring novels may not be so obvious.
Why is that?
Because the most chilling villains are those who are smart, could be the man next door, have vulnerabilities, strong motivation, are formidable, and their victims are real.
I remember reading a novel by Joyce Carol Oats titled Zombie. This was long before the current craze that has zombies the "in" thing to write about. She had used the term for her villain, who wasn't a zombie as you have come to expect. Oats was able to create a villain with all of the traits above and yet she made the reader feel sympathetic toward him. Not an easy task. However, I must admit I couldn't finish the book because her villain, frankly, unnerved me. I don't want to go into details because I don't want to give anything away, but oh my stars, as a parent I just couldn't handle it.
Believable villains are key to any novel. Just be aware that if your villains are especially bad and devious you might want to hold back for the readers who are faint of heart. You run the risk of them closing the book because they can't take it.
I'm just saying . . . do a good job, but also be sensitive to your target audience and what they will tolerate.
Have you read a novel with a villain that haunted you?