Jackson Chappell was a medical caretaker who worked for Bane in his senior years.
Chappell was hired by an elderly Bane to supervise his care and his estate. Bane's body grew weaker, evidently degraded by his constant use of the super-steroid Venom. Bane had grown so weak that he could hardly move, and needed a filter to breathe. Ironically, his body was so dependent on the drug that he needed it just to stay alive.
Until then, Bane kept the formula for Venom a closely-guarded secret, but to survive, he entrusted Chappell with it, just to keep his supply going. Chappell, inwardly corrupt, saw the chance to cash in and started a secret illegal business, dealing the drug in easy-to-use skin patches called "slappers" to high school athletes (and presumably others).
When Batman came to investigate Bane, Chappell feigned ignorance, but later on, Batman tracked one of his dealers back to his hideout. Confronted, Chappell confessed of taking advantage of Bane's situation to selling the drugs for profit. Deciding to take on Batman, Chappell used slappers on himself, increasing his strength many times and making him more than a match even for Batman's cybernetically-enhanced suit. However, Batman tricked him to tumble onto his own slapper-making machine, covering his whole body with the patches. Driven nearly insane with the pain of the drug, Chappell charged at Batman in rage, only to be blinded by some nearby chemicals. Swinging wildly around, he triggered an explosion in his own lab that knocked him senseless. The trauma of the blast, combined with the overdose of the drug, left him a brain-dead vegetable.
Powers and abilities
Chappell is an expert businessman who sells drugs for profit. After dosing himself with slappers, his strength increases greatly to the point where it exceeds Batman's battle suit enhanced strength and was able to shrug off Batman's punches with little to no effort.