All villains exist to serve a function of the plot. Only the great ones are compelling characters.
Strong characters are an essential part of good writing. It is through characters that the reader relates to what is happening in the story. A well-written character can forge an emotional bond, ramping up investment and propelling that page-turning narrative that every author hopes to write.
The obvious focus is the protagonist. A story without a compelling protagonist suffers from a profound handicap. Remember Thor: the Dark World? Show of hands who thought Thor was a more compelling character than Loki in that film. Speaking of Loki – let’s talk about the villain (or antagonist), arguably the second most important character when writing any kind of manuscript. Not every story has a romantic pursuit or friend, but antagonists play a central role in basic plot structure.
In every story, there is conflict. The protagonist is faced with a challenge and will either overcome or succumb to this as the narrative develops. While conflict and antagonist can be one in the same, they do not have to be. For example, in a story about a child defeating a bully, the bully is both the antagonist and the conflict. In a story about a woman searching for romance with a rival suitor, the romance is the conflict and the suitor is the antagonist.
When the antagonist is not the conflict, they usually serve to ratchet up the tension. To go back to my suitor example. The suitor entering would be a large part of the rising action. Pursuing romance was challenging enough, but another character raises the stakes. This all points to the role in the story that the antagonist serves.
Antagonists that only serve to fulfill a story function are usually very weak on their own. I’ve written about examples of this in the past: Hans (Frozen), Red Skull (Captain America), and even the villains in the recent film, Logan. I’ve also criticized video game developer Bioware on this on multiple occasions. If all the villain does is proclaim their opposition to the protagonist and celebrate their antagonistic ways, they aren’t likely to be compelling characters – or even characters at all.
The creation of a compelling villain begins with an examination of the protagonist. What is the flaw the protagonist is trying to correct/goal they are trying to achieve? An instant antagonist is a character seeking that same accomplishment. Examples of this include Raiders of the Lost Ark – a holy relic hunt where the villain, Belloq, is in pursuit of same desires as Indiana Jones. To keep on the Indiana Jones trend, The Last Crusade brings obsession in as a major character flaw. Indiana Jones is able to overcome this, realizing the value of other relationships in his life. The villain, Elsa, is not.
Another angle involves seeking to create an inversion of the protagonist. For example: Gaston is an inversion of Belle, both share outward beauty but their inner characters are complete opposites. Keep in mind, all of these villain creation angles can and do overlap. And none of these villains see themselves as the bad guy.
These are only starting points, however. A truly well-written antagonist still needs to follow basic character development rules. There are two approaches to this. First is the three-pronged character development scale (Competence, Proactivity, and Sympathy). The second involves the action–motivation-thought principle. Good characters have action, action comes from motivation, which is dictated by thought. An antagonist who stands around talking about how villainous they are is not contributing to the story, or to their character.
Unless the author’s goal is to have a vain, overconfident villain who sits back and expects everything to happen (think the Emperor from Return of the Jedi), this will not be interesting. That is the only instance where inaction is justified, because there it results from the character’s thought process.
Now, the good news is that – if you’re not a fan of villains/antagonists – you don’t have to spend a lot of time on them. While they do exist, they do not always have to be central to the main arch. The Witcher 3: Wild Hunt has a very simple villain without any complex motivations, but he is not central to the main conflict of the story (helping Ciri save the world). An antagonist only needs to be as big as the main plot demands.
Every time the antagonist is focused on, however, the author should strive to say something new about the character. Keep them moving, keep them developing. Static is boring. Keep their actions consistent and, most important, remember this: Character action should never be twisted to serve the plot, but plot can be changed to fit character action. Do not write a villain who acts wildly out of character every time the story demands it – in fact, don’t write characters like that. Period.