When batman carries out the joker, he doesn't respond to any questions from the chief dude (gordon?)
Anyways, although joker would have espaced and caused more misery, batman says he would have given him the cure.
Now, am i the only one thinking batman is sad that the joker is dead, it seems there relationship is kinda bound to each other. Like the constant cat and mouse game between them.
Maybe I'm way off, i just have that thought when he carried out the joker