Which is why Batman/Bruce Wayne probably constantly pushes for his rehabilitation and for Joker to stay in Gotham. But this is more headcanon than confirmed. I think it could be possible tho.
Batman and the Joker have perhaps the most complicated dynamic in all of comics -- and it's clear that they need each other more than they admit. Warning: contains spoilers for Batman #136! Of all the rivalries in comic books, Batman and Joker have the most brutal. They've been fighting for over eighty years at this point and some fans have asked why Batman doesn't just kill Joker.
DC has offered many answers to this question, but now the Dark Knight himself explains the real reason. Readers finally get a definitive answer to why Batman. What's the deal with Batman and the Joker? On a surface level their relationship is simple.
You could ask any preschooler who has ever watched a Batman cartoon and they'll tell you simply that Batman is the hero and Joker is the villain. Batman never killed Joker in the mainline story of Batman because he knows that doing so would allow him to sink to a level that's similar to the Joker. Remember that Batman has a moral compass, which means he doesn't want to kill criminals because he needs to do things correctly.
One of the things that people often think about the storyline of Batman is the dilemma between letting. Batman should kill the Joker. How many of us would agree with that? Quite a few, we'd wager.
Even Heath Ledger's Joker in "The Dark Knight" marvels at Batman's refusal to kill him. After all, the Joker is a murderous psychopath, and Batman could save countless innocent lives by ending his miserable existence once and for all. Of course, there are plenty of masked loonies ready to take the.
Batman is the one who jumps across the rooftop, but it's Joker who's the one who's afraid, who can't bear to bring himself to cross. Batman has to save the Joker when he can because it's the only way he can prevent him from being proven right, to prevent him from getting the last laugh. Batman and the Joker have one of DC's most brutal rivalries, with the Joker trying for decades to get Batman to see the "funny" side of life.
This might just be because Batman told the Joker his favorite joke during their first meeting, and the Joker was less than impressed. During their first confrontation, as explored in the story "Batman: The Winning Card" by Tom King and Mitch Gerads in. However, there's one villain that many think Batman should make an exception to that rule.