A villain whose methods are wrong but whose motivations are understandable, noble, or even sympathetic.
An antivillain is an antagonist who possesses heroic goals, genuine virtues, or sympathetic motivations despite being the opposing force in the story. Where a villain is defined by malice and an antihero is a flawed protagonist, an antivillain occupies the mirror position - they're on the wrong side of the conflict, but for reasons the reader can understand or even respect. They challenge the idea that opposition to the protagonist automatically means moral failure.
Antivillains elevate your story beyond simple good-versus-evil. When readers genuinely understand why the antagonist does what they do - when part of them even agrees - the conflict becomes richer and the themes more interesting. Stories with antivillains force readers to think rather than just cheer for the hero, and that's what separates memorable fiction from forgettable fiction.
Inspector Javert is one of literature's great antivillains. He pursues Valjean relentlessly not from cruelty but from absolute faith in the law. When he realizes the law can be wrong, it breaks him.
Severus Snape spends six books as an apparent villain before the final reveal reframes his every action. His cruelty was real, but so was his sacrifice.
Several antagonists in the Broken Earth trilogy are fighting for the survival of communities or species - their opposition to the protagonist stems from competing visions of what survival looks like.
Victor Vale is simultaneously protagonist and antivillain, seeking revenge through methods that are clearly villainous while maintaining a moral code the reader can follow.
If the antagonist's position is entirely correct, your protagonist doesn't have a real conflict. The antivillain should be understandable but still wrong in some meaningful way - or right about the problem but wrong about the solution.
A sad origin story doesn't automatically make an antivillain. The character needs present-day virtues or a defensible moral position, not just past trauma.
An antivillain still needs to be a genuine threat. If they're so sympathetic they never do anything truly harmful, they're not really a villain at all - they're just a misunderstood friend.
Take a villain from something you've written (or from a favorite story) and rewrite their pivotal scene from their perspective. Give them a clear, logical reason for their actions that doesn't rely on cruelty or insanity. Make the reader think, 'Actually, I might do the same thing in their position.' That's your antivillain.