Think of your favorite show, or book series. More specifically, think about the villain. Think back on every terrible thing they’ve done.
Now, ask yourself why they’ve done those things.
If your first reaction is to say because they’re evil, or because they’re terrible people, or any reason that can be boiled down to ‘just because’ stop. If you can at least guess at their motivations or reasons such as greed or revenge, then you’re good to go: you have a fully developed character for an antagonist.
Whenever you come across an antagonist in a story—your own included—they should be just as developed as any other character. This means they have a backstory, they have motivations and they have goals. Because antagonists most often show up as the villains of a piece, it’s too tempting to say they’re doing things just because they’re bad. People don’t like doing bad things, so he or she must be doing these things just because they’re bad, right?
Even someone terrible enough to properly earn the title of villain has a reason for what they do. They may not have the moral high ground, but they do have motivations and reasoning to make them choose the terrible instead of the ethical.
Take a look at your own antagonist. Ask yourself the same questions about them that you would about your protagonist or any of the supporting characters. What are their long term goals? What are their short term goals?
What obstacles do they have to solve to achieve those goals?
Now take it one step further. Ask yourself why they want those things. Don’t automatically assuming their logic is twisted either—your antagonist might be trying to get in the way of your romantic couple because they feel they need to protect one or the other from what they perceive as a bad choice. Similarly, your antagonist might want to kill the king because he feels the king is abusing his power.
Don’t forget backstory is just as important your antagonist as it is with any other character. Consider what their family life was like, where they grew up, what hardships or ordeals they’ve faced.
It’s also worth noting that two of the more common tropes in antagonists is either mental instability or abusive backgrounds. While these are tragic and often difficult topics, keep in mind that they’re common tropes and potentially harmful. Think of the people you know who struggle with mental illness or who have come from traumatic childhoods. They probably don’t go around doing things to hurt people or animals on the regular, which makes using it as a reasoning for your antagonist weak and unrealistic.
What motivates your antagonist? Let me know in the comments!