1. The adversary of the hero/protagonist of a drama or other literary work.
Antagonists are an important part of any story; in any medium you are bound by the fact that every hero needs a villain. Of course, a lot of people forget that the villain needs to be just as well thought out and explained as the hero of the story. So there are a few things to think about when creating your anti-hero. Are they three dimensional? Do they have a reasonable motive? Do they have traits outside of the relationship with the protagonist? Are they taken seriously? These are all very important to keep in mind when creating an antagonist.
Is your character three dimensional? In other words, is he/she more than a baddie? Are they complex and have successes and failures in their past? Do they think in a different way than most people? Little quirks and compulsions they have should be known. Speech, ticks, the way they sit and stand. Create them like you would create your hero, they deserve just as much attention to detail. An example of doing this correctly would be the Goa’uld from Stargate SG-1. They have a developed culture and each of the baddies are bad with no real apologies, yes, but they have failures and successes, they are each well thought out characters.
Do they have reasonable motive? Now, it may not seem reasonable to everyone (considering mental processes and logic patterns can differ as can morality and judgments), but if it seems reasonable to the antagonist and that is explained somehow, then that is a good enough motive. How can you develop this? The question to ask is what was the trigger that made the baddie turn so… well, bad? Was this a long time ago, or recently? Usually a good motive, if you’re having trouble thinking of one, lies in the following: sex, money or power. It could be any combination of the three, so don’t necessarily confine yourself to just the one. An example of this done correctly was Voldemort from Harry Potter—while the rest of his characterization may have been shallow and flawed, the audience definitely knew why Voldemort became what he did. He had a background, a history that defined him and shaped him into being, and then there was the trigger of the prophesy to get him all riled up, hence the Harry Potter series.
Does your antagonist have traits outside of the relationship with your protagonist? For example, does he think about things without the ulterior motive of taking down the protagonist interfering or influencing him in some way? Can your antagonist do things without it having to further the plot or have something to do with the main plot (ie. Can he enjoy a spot of tea? Does he have a family that doesn’t know he’s a baddie?) Not everything contributes to the overall plot, and that’s perfectly okay. An example of this is seen in Game of Thrones, as Cersei Lannister is widely accepted as an antagonist, however she has traits such as being a fiercely protective mother; being in love with her twin brother, that have nothing to do with any of the would-be protagonists.
Is the antagonist taken seriously? If they aren’t, why aren’t they? Will that change? If they are—how come? How have they affected or negatively impacted the world around them? These questions should be easily answered once you have your motive and have thoughtfully made your character into one that is a good match for your hero. A great example of this is actually Megamind; as he wasn’t taken seriously in the beginning because he was not negatively impacting the world around him in any way that the hero couldn’t fix in no time. He was well thought out in this stage of development and brought a lot to the film, even in the beginning.
All of these questions should help to form a well thought out antagonist who is worthy of being a part of your story. If you leave questions such as these without answers it leaves the audience still asking them—but to no avail. If they don’t know why your character is being a bad guy, then it seems to be without meaning. If your character is one dimensional then they are easy to defeat, and therefore not a real threat to the protagonist. So you see, it’s of import to create your antagonist in a loving, nurturing way. After all, they are there to play a large role in your universe, so give them the tools to do so.