The Batman Who Laughs: The Full Story
7. How He Became The Batman Who Laughs
Bruce Wayne of Earth -22 was already something of a loose cannon, but he was about to be pushed over the edge.
The Caped Crusader was captured by Joker and subjected to the beatdown of his life. In true Joker style, mere physical pain wasn't enough and he let Bruce in on his new, villainous plan. While still tied up, Bruce could only watch as the Joker proceeded to recreate the night his parents were killed, shooting multiple parents and infecting the new orphaned children with Joker Toxin.
This was the breaking point for Bruce, who broke out of his restraints and finally put an end to Joker's sick life. Unfortunately, the Clown Prince had one more trick up his sleeve, as with his dying breath he released the toxin contained inside of him directly in Bruce's face.
The transformation Wayne went through as the toxin corrupted him was a slow one, and allowed him time to plan for his inevitable demise, training up the Bat Family in the hopes they could stop him.
It was ultimately useless though, as they didn't even get a chance to try. The training session was a trap, ending with Bruce killing the entire family with a hauntingly familiar smile coming from his mouth.