The Joker escapes from Arkham Asylum. He kills a few people in clever and macabre ways until Batman punches him in the face and takes him back to Arkham.
I’ve seen this cycle so many times that Batman feels like an accomplice. He’s the guy that gives the Joker a ride home at the end of the day. And why not? The Joker’s much more effective at advancing his agenda (kill people) than Batman is at his (save people). If you can’t beat them, join them. That’s the Wayne family motto.
Since the villains are just as valuable as intellectual property as the heroes are the best the hero can aspire to is maintaining the status quo. After racking up a body count in the thousands there’s no reason why the Joker’s still alive except that he looks good on a t-shirt or in a video game.
There are no character arcs here. DC and Marvel have these vast universes of static characters where change is either illusionary or temporary no one’s really fighting for anything. And since they’re also immortal then there’s no good guys or bad guys. Just two armies of vikings, fighting it out in Vallhalla till Ragnarok hits the publishing industry.