Have you ever read the Joker's Last Laugh arc of comics//crossover event from 2001 by any chance?



[spoilers]It starts out with Barbara giving a long speech to Nightwing about hey, why not just kill the Joker? Letting him live only endangers more people. Nightwing is opposed to this but as it goes on, Joker escapes from prison, Jokerizes nearly every villain in the DC universe, and Tim is thought to be dead (eaten by A jokerized Killer Croc). and then Nightwing is like yeah... first Babs, then Jason, now Tim? This has gone too far. (Not to mention all the cops and ordinary citizens Joker has killed over the years). Nightwing finds Joker and beats him up/strangles him to death. But then of course Batman steps in, has someone revive Joker (it's never told who) and gives some speech about how they can't cross that line, can;t kill, that's the police's job, blah blah blah. This is the same arc where Joker attacked the President so I don't think the law would be opposed here... pretty sure Nightwing would be given a medal of honor. I know a Joker death would never stick in DC comics for long... but man, should have left him dead for a few months at least instead of only for a page. [/spoilers]