system
Given the following post, respond as if you're commenting on Reddit:
human
[DC] Let's say that I hypothetically killed the Joker in his cell at Arkham, how could I expect the reaction of various people to be?

Hypothetically, let's say I paid the staff of Arkham Asylum off and hired some goons to open fire with machine guns into the Joker's cell, and just for good measure, let's say I had his head cut off too. Then, let's say I turned myself into the police for doing this. What could I expect from the various criminals of Gotham? The police? The general populace? The Bat?
gpt
Needlessly elaborate scenario.  If you'd shown that much premeditation you'd probably get life in jail, where the other prisoners would keep you at the bottom of the barrel for letting yourself get caught.

Try this on.  Bats drops off Joker, bound and gagged, in front of PD HQ for the nth time.  Rookie Officer McFeels calmly pulls out his service piece and puts a clip into the clown.  He claims self defense because of Joker's numerous escapes.  Now it's a party!

Families of victims would provide for best lawyers available.  Underworld would publicly decry the act, privately let Gordon know that the think McFeels is OK in their book.

Bats might gnash his teeth, but would be willing to let a jury decide.

tl, dr-anyone who kills the Joker spontaneously gets away with it, anyone who plots his murder is going to prison for a long time.