This will be specifically addressing this line said by Joker in the Dark Knight.
The Joker: [while hanging upside down] Oh, you. You just couldn't let me go, could you? This is what happens when an unstoppable force meets an immovable object. You truly are incorruptible, aren't you? You won't kill me out of some misplaced sense of self-righteousness. And I won't kill you because you're just too much fun. I think you and I are destined to do this forever.
With this in mind the flaw of Batman is that he won't do whatever it takes to do what is right. He won't murder a person who will only bring harm to this world instead breaks a few bones then waits for them to be a problem later on. Sure in the movie he died I think or maybe because of Heath Ledger's death they removed him the the last movie but Batman didn't end his life. If the problem was ending someone's life Batman sure doesn't mind ending the life of animal when eating it for dinner. Doesn't directly happen in the movie but in other media it has. So basically Batman is okay with taking the life of an animal if it is not directly responsible for it but is not okay with directly taking a life. The problem here is that the animal still is dead and Batman benefited from it. If Batman murdered the Joker every single person who could potentially die because of the Joker at the very least would be the prison guards would not die and the people who died in the past will be avenged. Guess Batman is not a utilitarian.
What does anyone else think?