Last week I talked about the protagonists of your story. This week it’s all about the antagonists, something that new writers tend to overlook. But for a book to have a hero, it needs a villain, and they need to be as deeply developed as the main character with their own wants and desires.
The key is that these wants and desires need to be the polar opposite to those of the protagonist. Or maybe they match, but the way the antagonist goes about trying to obtain them is against what the hero stands for.
Author Liana Brooks has a three villains theory: an immediate, an intermediate, and the big bad. You can read more of this theory here but if we take Harry Potter as an example, the immediate villains are the Dursleys, the intermediate villains are Draco Malfoy and (apparently) Snape, and the big bad is Voldemort, who during The Philosopher’s Stone has possessed Professor Quirrell.
If you’re writing a romance, your love interest can be the immediate villain. This trope is known as “enemies-to-lovers” and is one of my favourites. I love watching two people go from bickering to becoming friends and then more!
You can also have a twist where the big bad has seemed to be on the side of good for most of the novel. Raistlin Majere from the original Dragonlance series springs immediately to mind. Whether the switch is as bleeding obviously coming or more subtle is up to you.
The main antagonist tends to have co-conspirators / underlings, who all need their own reasons for siding with the bad guy. These could actually be good reasons, with good intentions. But that is what the road to hell is apparently paved with.
The trick to believable bad guys is to avoid having them bad for the sake of it. Give them layers. Have them do good things. The reader should understand – and even empathise – with your villain, while rooting for the good guy to triumph.