this is actually going to be the batman who laughs... i like the concept of him, he is a batman from another earth that figured out that the joker on their world was killing kids parents in front of them, being that this happened to batman, Bruce snapped and killed him, but the act of him breaking his one rule, joker had a backup plan, he released a neurotoxin that made him the new joker... the legacy of the joker shall carry on, he has killed every hero and villain, meaning he is the apex being in that universe