10 Times The Joker Actually SAVED Batman
4. Killing Alexander Luthor
The sole survivor of Earth-3 during its storyline, Alexander Luthor is the son of Lex Luthor and Louis Lane and remains one of the most sinister villains in the world of DC Comics. The man responsible for killing Super Boy and seriously maiming Nightwing during his final battle, he shares the same kinds of arrogant traits as his father, as well as his trademark stubbornness.
Such is the chaos and destruction Alexander is able to cause during his time on Earth Prime that it drives Batman to the point where he looks certain to break his one rule for him. It's Wonder Woman on this occasion that stops him from doing it, but The Joker is soon on hand to ensure Luthor Jr. is brought to justice.
Once again all too aware of Batman's rules and breaking points, The Joker saves the Dark Knight the task of killing a baddie in one of the most brutal sequences in the two characters' histories.
It's another glaring example of how the two have been able to keep each other going for so long, but also how The Joker's twisted psyche keeps Batman from really spiralling out of control.