Villains are more interesting than heroes in a lot of ways.
Heroes have rules they follow. Lines they cannot cross. They are bound by moral choices and expectations. They always have to strive toward what is right, even when it costs them something personally. Heroes fight themselves constantly. They wrestle with guilt, morality, responsibility, and the consequences of their actions.
Villains don’t.
Villains act on impulses.
The same impulses everyone has buried deep down inside themselves but cannot express. Pride. Jealousy. Anger. Hatred. The need for power. All powerful emotions that most people suppress every day in order to function within society.
But villains get to act on those impulses.
Everyone has moments in life where they want to give in to anger or lash out without restraint. Villains have the ability to carry those feelings out without hesitation and without consequence—at least until the hero arrives.
One of the purest and most recognizable examples is Darth Vader. He kills officers who fail him without hesitation. The brutality of it is horrifying to any normal person with a healthy emotional range. But underneath that horror is something strangely relatable. Everyone has dealt with incompetence before. A bad employee. A terrible boss. An irritating coworker. The villain gets to express the frustration people fantasize about without restraint.
That is why villains are so compelling.
They are also incredibly fun to write because you get to dive into the psychology of someone unrestricted by morality. Villains can be unpredictable for no reason at all. They can be cruel, charismatic, petty, intelligent, childish, manipulative, or terrifying all within the same scene. They do not need to justify themselves to anyone.
Heroes do.
Heroes constantly have to justify their actions so the audience understands and sympathizes with them. They often remain confined within the moral framework of their story, while villains are free to move outside of it.
But without heroes, villains are just monsters.
In the end, villains give in to primal instinct. Heroes resist those same instincts.
And without a great villain, a hero is nothing.
Without Darth Vader, Luke Skywalker would just be a whiny farm boy staring at twin suns.