I think that Harley killing the Joker would have the most potential story-wise and would make the most sense.

we ail know It Will never happen anyway

Harley, I think it would be cool if another villain was the person to finally kill him.

Harley! It'd be extremely interesting to read!

Todd is the obvious choice. Harley would never even though it'd be great.

There is only one and it should be Bruce. But it doesn't matter cause even if he dies he'll comeback.

The Joker Will Kill The Joker!!!

Harley

Didn't realize I already posted in here but still, out of the choices im going with Harley but id like to see a new villain come out of nowhere and brutally kill him, maybe string him up somewhere in the city for all to see. That would be quite a statement IMO

Todd

Jason Todd.

Batman is the only one Joker would allow to kill him. He's too smart for anyone else

Harley killing the Joker is totally against everything that character is.

Harley doing it would make the most sense and would be the best story. Babs already got her revenge on joker and a simple revenge story isn't interesting. Jason didn't even really want revenge against joker, he was more mad at batman. Harley doing it would be awesome. I wouldn't mind batman doing it by accident

Harley

It could be that Joker seriously hurts/tortures/kills another member of the bat family and Jason decides enough is enough and if Bruce isn't gonna do anything to finally stop Joker than he will.

Harley killing Joker would be the worst thing to happen to the character, Joker is literally the only thing that makes her interesting.

Turns out the guy to do it was Talos. For the pre-flashpoint version.