Joker didn't break Batman. True, he turned Dent, but Batman retired because he was no longer needed. He let the Dent act take over and the police handled most everything from there. Batman isn't Spiderman, he doesn't go after every thug himself. Joker wanted to show that the people of Gotham were all bad, and, as Batman pointed out at the ending when the boats didn't blow up, they're not. Despite all the fear and panic he put out there, despite all the bullying he did, the people resisted (generally speaking). Furthermore, the Joker wanted Batman to kill him. That was his main goal with Batman; it was never accomplished. This is definitely more proof that he never beat Batman. When Bane emerged, he took over Gotham. There is no denying that. He had tanks patrolling, Batman's back was broken (and he was in prison), and the city tore itself apart in an Occupy Gotham-esque style. Yes, Batman re-emerged and was able to win in the long run, but no other villian did what Bane did in completely defeating Batman like that.