The clown prince of crime is known as one of the the violent villains in all of comic books, but what is the worst thing this Batman Baddy has ever done? WatchMojo presents the top 10 Worst Actions the Joker has ever taken against the Dark Knight. But what will top the list? The Death Of Jason Todd, The attack on Barbara Gordon in The Killing Joke, or the constant abuse of Harley Quinn. Watch to find out!