When designing your story, it’s essential that the type of villain you’ve created fits with the genre you’re working in.
For instance, you probably wouldn’t put a werewolf in a drama like Citizen Kane, and if you did, it certainly would no longer be a straightforward drama. That’s why I recommend that you spend some time to precisely determine the genre of your story, and to do this I suggest going to Netflix or some other large library of movies. Check out all the genre categories and see which one your script most resembles. Once you’ve done that, download as many of that type of movie as you can and watch them carefully, paying special attention to the nature of the villains, how they are created, and what the similarities and differences are within that given genre.
Next, take all the information you’ve gathered and try to give your villain a good solid twist, something that differentiates him or her from the pack. Remember how tender Don Corleone was with that cat on his lap? But the proper balance is crucial. You want to go against type but not too far—after all, you don’t want to break the rules of your genre or create a tone that might confuse or scare off fans of that kind of story.
Finally, humanize your villain with a compelling backstory. Keep in mind that your villain needs to be as fully fleshed-out as the rest of your characters, whether we’re talking about a crooked cop, an evil C.E.O., or Frankenstein’s monster. Did your villain have a family? Where did he or she grow up? Has life held disappointments that bent his or her psyche? Most powerful of all can be a previous personal relationship with your hero. Were they best friends as children but parted ways? Were they in the army together? This kind of connection between the past and the present can make for a particularly personal and powerful conflict.