The antagonist or antagonists of a story are often the central driving force to the story or what causes the central driving force to come into being. That being said, a lot of thought has to go into creating an antagonist, especially the central antagonist. In fact, for horror novelists such as myself, it’s often one of the first things we come up with in a story, and what we often use to describe our stories to others (ex. “an evil clown demon terrorizes a small town”, “a cult leader with horrifying dark powers and those who stand against him”, “two children fall through a doorway to a world where the demonic ruler has a terrifying interest in the young boy”).*
When designing antagonists (human or otherwise), there are a few things I try to keep in mind in order to make them as evil/terrifying/monstrous as possible. Here’s some of them (the ones I’ve identified, anyway. I’m still new at this and I’m still identifying what I do, what works and what I should probably stop doing):
1. What does your antagonist want? I’m going to use a villain from a hypothetical novel, because I don’t think this is the best place to advertise any of my own books(as fun as that might be). And since I’m watching Once Upon a Time while watching this, I’m going to say…my villain wants to take over the magic kingdom. Why does this villain want to do it? Perhaps he’s a sociopath (I’m going to make it a male villain) who just wants power, mayhem and murder. Perhaps he’s the illegitimate child of the King’s eldest daughter, there was a really bad scandal where they murdered to keep things under wraps and he’s got some mommy issues. Or maybe he’s thinking he’s doing the kingdom a favor by trying to avert a prophecy about the current regime and the destruction about the kingdom, so he’s willing to do some very terrible things to avert disaster. Any of these or even a combination could work. This is also a step where I try to create as much backstory as needed to explain how my villain came to be, though if I need to I can hold that off till much later in the story, when it becomes much more relevant to the story to explain why my villain is so evil and screwed up.
2. What are my villain’s means of getting what he wants? Every villain has a means of getting what they want. Maybe he’s a very dangerous, highly-trained assassin. Perhaps he has magic powers, or a mercenary army with enough magical weapons to do a miniature Chernobyl. It can be anything, as long as you can make it plausible in the universe of your story.
3. Who opposes my villain? I’m going to assume the protagonist. Perhaps it’s the crown prince of the kingdom, who just found out about his elder sister’s illegitimate son and sworn to stop him but bring him back alive for the sake of his sister, who has always regretted letting her child go. Or maybe a knight who wants to protect those close to him by going off to slay the great evil. Perhaps it’d be more interesting to see if an orphan of humble background (or perhaps not; s/he is an orphan, so s/he could have any background I please) could go up against this great threat to the kingdom. In any case, the antagonist needs someone to go up against him, so I have to create that person at some point early on.
And now that we’ve come up with the antagonist’s motives and who’s going to try to stop him. Here comes the fun part of designing the antagonist:
4. Design your villain’s character. Perhaps my villain will be a full adult, or perhaps a teenager or even a young boy, to drive home that he’s the son of a princess, son being the operative part here. I could give him a dark, sadistic personality. Or maybe he’s like one of my favorite villains, Mayor Wilkins III from Buffy the Vampire Slayer, who always had a smile on his face and acted like your typical 1950s sitcom dad even up until the moment he killed you. Maybe he’s got a hobby that indulges in while he’s not busy planning the destruction of the kingdom. Does he actually care for anyone besides himself? Maybe that person would give him someone to interact with besides his despicable followers. All these options and more are at my fingertips, and I can mix and match as I please in designing this villain.
This is basically how I design villains. And it works for all types of villains, from primary to tertiary in importance of plot and in all types of stories. I could also use these steps to design a sultry heiress hell-bent on doing some nasty stuff in LA’s best social circles. Or maybe a company president with some very cruel plans for a Native American community in the Amazon. It even works on zombies and vampires, too.
However you create your antagonists though, if it fulfills your need to create a great villain to go up against your hero or heroine, then it works. I’m just trying to give helpful suggestions, and if these help you, then my job here is done.
Also, if you get inspired by the hypothetical story I created above, by all means write a story about it. I just came up with it on the spot and I have enough on my plate without another story to write. Go ahead. It’s yours.
*Only one of these examples is a story I’ve actually read, and that’s Stephen King’s IT. The other two, if there are stories that are like that, I haven’t heard of them. Let me know if you have.