I feel like not killing the Joker, at a certain point, is just negligence. I'm not condoning vigilante justice or murder, but eventually they've got to go. The arch nemesis has to be put down. I mean, Moriarty was only ever in two Sherlock Holmes stories, and he died and no one complained about how he should have been around longer.
Pretty much after what he did to Barbara Gordon -- Like. Doing things by the "book" and bringing him to justice -- I'm sorry. No.