Anyway, Bats killed Joker on that end panel? So how come he's still alive? (not trying to dispute it, just curious) isn't the killing joke canon, with Babs actually becoming wheelchair-ridden after it?
Superboy Prime punched a wall.
Really, though, the ending is ambiguous on purpose. This is Alan Moore, after all. After writing the final Silver Age Superman story in which he combined Supes's two worst enemies (Luthor and Brainiac) into one creature and turning Mxyzptlk into a Bruce Dern looking psycho, why would he not take the chance to write the ultimate and final Batman/Joker confrontation. But it's work for hire with DC's money makers, so he just skirts around it.
