The Dark Knight Rises: What makes the Joker’s character so effective?

The Joker says things like: “Hit me, come on hit me” and “You have nothing on me” The Joker knows that Batman’s moral code is not to kill. So, the Joker fully knowing this, can test the Batman to his limits. The Joker doesn’t care if he dies. In fact, the Joker wants Batman to kill him because this would break Batman’s moral code and chaos would ensue in Gotham and the Joker's legacy fulfilled.