Friendly Enemy

"[Aziraphale was] The Enemy, of course. But an enemy for six thousand years now, which made him a sort of friend."

- Crowley

One of the most fun on-screen relationships antagonists can have isn't white-hot hatred, deep-seated revenge, or even bitter contempt, but... friendship.

Over the years, a Hero and his nemesis will share trials, failures, and successes at each other's hands, each becoming enormously important in the other's life and more intimate (not that kinda intimate! ...Well, sometimes) than many best friends. Over the course of a series' many Story Arcs, the two will develop a grudging respect for their Worthy Opponent. It can sometimes grow to the point that the villain will refrain from killing the hero in a "cheap" or dishonorable way, and even start to concoct bizarre excuses to avoid doing so entirely, spare his life, or even saving him. In these cases, the hero and villain are very likely to become Strange Bedfellows to beat a new villain who doesn't play by the rules, which may lead to Fire Forged Friendship. Sometimes, the villain will decide to admit to the friendship and perform a full Heel Face Turn. If, another villain kills the hero, this one may make sure that the hero doesn't die alone, and the hero will do the same for him.

Even if the villain doesn't switch sides, it's not impossible for both to be friends "off the clock", or take time out of their latest fracas to Go-Karting with Bowser, or share a meal, or run errands together.

Other times, the opposite happens. A Genre Savvy villain will notice that this is weakening him against the hero, and he'll promptly jump off the slope that they've been slowly climbing and undoing Seasons worth of Villain Decay by doing something truly vile, like stuffing the hero's girlfriend in a fridge, or just plain pulling out new and lethal tactics when the hero is expecting the same old Harmless Villain. The above trope is common enough that the subversion is becoming a normal trope in and of itself.

In these relationships, the hero rarely stops trying to catch the villain, while simultaneously making his capture a personal quest or mission. Needless to say, humanizing a person whose capture you've objectified can complicate your priorities.

Related to Worthy Opponent. Contrast It's Not You, It's My Enemies, Big Bad Friend, and With Friends Like These.... See also Did We Just Have Tea with Cthulhu? See Dating Catwoman for the (explicitly) romantic version. Often goes well with Antagonist in Mourning. Frequently the target of Foe Yay.

Essentially, platonic Foe Yay.