A great literary villain is not any one thing; some are moustache-twirlers or evil geniuses, some are darkly complex, tortured souls, while others are amoral crazies who act wholly on impulse. There are many ways to write a literary villain, but a unique characteristic often binds the truly memorable anti-heroes together: they are at least as complex as the heroes.
Some of the earliest and greatest literary villains come from William Shakespeare. While literature certainly featured villainous characters before, Shakespeare had a talent and interest in developing their characters and the motivations behind their evil actions. In Othello, Shakespeare gives us possibly the most iconic literary villain of all time: Iago. The play revolves entirely around his schemes, and Iago frequently speaks to the audience, explaining himself and his plans. This tradition of a “thinking villain” has influenced many writers throughout history, and led to the creation of dozens of famous literary evildoers.
A great literary villain can be almost entirely pure evil; in the revolutionary Harry Potter series, much of the climax depends on the idea that the villain, Lord Voldemort, is truly unredeemable and beyond help. Yet the simple motivation of gaining ultimate power is the most basic thing about Voldemort; what makes him a compelling villain is the meticulous explanation of his past and rise to power. The depth of his villainy makes him a powerful and memorable figure, one that will haunt the nightmares of many for a long time to come.
Other villains are complex in their seeming amorality. These characters are particularly frightening as they seem to live chaotically, choosing actions by impulse or for their own highest good at any cost. Sometimes, these characters are described as gray- or anti-villains. They will occasionally do good, if necessary, but can very suddenly decide to do evil or actions that are detrimental to the hero. The random-seeming pathos of these villains is unnerving and memorable, as the challenge the concepts of ordered systems by their very existence.
A good literary villain can also be one with motivations or characteristics that are both easy to identify with, and to a certain extent, universal. Creating a villain that is sympathetic gives readers a powerful contradiction of emotions. While they do not want the character to succeed in their dastardly plans, they feel true remorse for the pain or fatal flaws causing the villain to react with evil. In Macbeth, the villain arguably does a good thing, by ridding the kingdom of a weak and frail king and replacing him as a hero of the nation. Yet Macbeth is twisted by his own love of power, and, almost against his own will, falls into darkness.
For the most part, the best literary villains remind us that they, too, are human. No matter how twisted or dark they might be, they are not so different than you or I. The paths that separate the hero from the villain are complex and uncertain, and great writers are often able to accurately depict not only the evil done, but the humanity abandoned.