8. Teaming With Batman
Proving that the only thing Batman and Joker dislike more than each other is a person who is both of them combined, the mortal enemies join forces in order to fight the Batman Who Laughs within the pages of Dark Nights: Metal.
Given that canonically this comic follows just after the Endgame series - a storyline that sees the pair actually kill each other (although it doesn't last) - it takes some pretty heroic chops on the parts of both the Joker and Batman to put aside their differences in order to save the day.
The fight shows that - despite Joker's homicidal tendencies - he isn't as lax about the fate of the world as you'd expect, and that he actively wants to save the world when the person threatening it isn't him.
It's always fun to see the Clown Prince of Crime and his beloved rival team up, but usually it is somewhat begrudgingly on both parts - whereas Dark Nights shows a duo that is willing to join forces without even discussing it when their world is placed under threat.