He had help in Knightfall, even before he broke out all the criminals in Arkham with his bazooka. After Batman was drained, he then knew who he was, and went to the manor to break his back.
So yes, he broke his back by himself, but he had help with the breakout, and of course, had help with draining Batman with all of Arkhams inmates.
He wasn't alone, but he was the leader.

at the logic. But - to each his own.