I was telling Tegid a few days ago about an approach to Bane I made up knowing very little of the character. Him could be a young man (or even a teenager) from the slums, extremely intelligent and quite fit, but with a terrible life, a drug addiction and feeling grief stricken from his parent's death by some criminal.
He becomes the first Robin, and everything seems to be working fine until he starts using lethal force to kill Gotham's criminals and abusing an experimental drug that gives him incredible stamina and pain tollerance. Batman's justice and his own collide, and he decides he has to get rid of Bats to really bring justice to Gotham and avoid anything like what had happened to his parents to happen again. This way we have an "evil" batman who is as intelligent as Bruce, or even more, stronger than him and bent on his destruction. And that is actively plotting to kill him.