Oh who cares? I've been blown up, thrown down smokestacks, fed to sharks; I'm the Joker! I always survive!
—The Joker from BatmanMusic to listen as you read the article
Face it, some Big Bads stay popular enough it might be a bad idea to kill them for real. So they may stick around or keep coming back, but too much of this can start to undermine a hero's perceived effectiveness. While a work focusing on a single hero or group can Hand Wave this as perhaps what's necessary to end the villain for good being beyond their moral code, it can get more egregious if the fictional universe starts to get larger and more interconnected, and the villain keeps ticking off more and more people. This leads to the question of why some of those other folks with a lot fewer qualms against killing haven't got rid of them yet.
This ends up being a question of whether the villain is just that good, or the writers are delaying things and stretching the patience of the audience.
side from rationalizations given in the story itself, most reasons for trope are outside the story in the form of Contractual Immortality:
• The villain is very popular and lucrative, so franchises with indefinite continuity are hesitant to get rid of them. Particularly writer's dreams of writing a good villian story and to get rid of him with any sense of finality would seemingly rob future writers of such a coveted opportunity. Ironically, a villain could be ostensibly lame, and killing them off is seen as too 'serious' a treatment rather than just putting them getting out of town.
• The story exists in a particular continuity or on a sliding timescale; the actual time the villain has been around for a particular story may be smaller than we suppose. it may seem like the Villian's been using mass destruction for however-many-decades in Real Time, but in the comic book universe it's only been a handful of years at most.
• The villain, especially those in a Rogues Gallery, are so heavily identified with a particular hero their exploits are specific to him out of a kind of authorial respect.
• The struggle against a single major villain is the Series Goal and if that villain is defeated, the series would be over. If this is the case, then the Grand Finale will occasionally revoke Villian Immunity.
• The series is being shown in Anachronic Order, and their death has already been shown. This can apply to any character, not just villains.
Personally I think this is kind of stupid and annoying because why just leave the villian alive so you can use him in the next story.
What do you think?