10 Shocking Times The Joker Died
4. Endgame - Batman #40
In the story, Batman: Endgame, the Joker infected the Justice League and the citizens of Gotham with the most dangerous form of Joker Venom; a concoction that forced the victims to kill the people they love the most.
Batman learned that the toxin's effects could be reversed using a liquid metal called Dionesium located in a cavern under Gotham. Not only can Dionesium heal any injury, it can regenerate dead tissue and thus, bring people back to life.
When Batman located the Dionesium pool, the Joker tackled him, and the two squared off in an epic battle. Their brawl was so intense, the cavern collapsed and destroyed the Dionesium cache.
Just before they died from their injuries, Batman told his mortal enemy that he failed since the Dark Knight created a vaccine from the Dionesium, which discharged throughout Gotham, curing everyone from the toxin.
Batman and the Joker perished, but were revived since they were exposed to traces of Dionesium in the cavern. Because they only made contact with a small amount of this mysterious liquid, the pair also lost their memories. When they regained their memories several months later, the two returned to being the bitterest of enemies.