Killing Jason Todd
Leading up to Batman #428, the Joker had done many things to irk and annoy the Caped Crusader over the years. However, nothing could’ve prepared Batman for his most sinister act yet: killing Jason Todd, the second Robin, in shocking and gruesome fashion.
This was a true turning point for the character, as it showed how despicable and nefarious he could truly be despite his smile and ha-has. It’s easily the pivotal moment that elevated him to the pantheon of great villains. Sure, Jason was a whiny sod and we did technically vote for his death, but man, Mr. J was unrelentingly brutal here.
Furthermore, if you’re looking for the one event that solidified the Joker as the Dark Knight’s greatest foe, look no further. To this day, Batman still feels responsibility for Jason’s murder, even more so than his parents’. This one hit hard, and it was all the clown’s doing.
Making Batman Laugh
When you think of Batman, you don’t associate him with humor or good times. In fact, he’s probably the sort of guy who ends up patting the dog at the party and driving all his drunk friends home. That said, the Joker did make him laugh with one of his stupidest jokes, ever.
In the finale of The Killing Joke, after all the havoc that the Clown Prince of Crime has caused to Bats, Jim, and Barbara, he tells his arch-rival a silly joke. Once he’s done with the punch line, he giggles to himself about it – and surprisingly, so does Batman.
What happens afterwards is still a debate to many, as some believe the Dark Knight finally broke his steadfast rule and ended his foe. However, this isn’t the point here. What does matter is that the Joker turned Batman’s frown upside down with his comedy.