Bane

Bane is one of Batman's most strongest foes, due to the formula called Venom in his vains

Becoming Bane
A nameless man was volunteered in a Cuban prison experiment code named Project Gilgamesh. It was a government sponsored program designed to use a special chemical called Venom to engineer an army of super soldiers. However, this man had other ideas. Physically enhanced by the Venom, he broke free of his restraints and escaped. Three years later, he began to call himself Bane and hired himself out as a South American hit man.

Confronting Batman
Bane was hired by the Gotham mob boss, Rupert Thorne to kill Batman. Bane agreed and secretly planned to also kill Thorne and take over his rackets in Gotham. Bane kidnapped Robin (then Dick Grayson) and lured Batman to a showdown which ended when Batman overloaded his Venom intake. Candice, Thorne's personal assistant, was implicated. Bane remained in Gotham and attempted to establish himself in the criminal underworld. Bane has since then teamed with the likes of the Riddler, Mad Hatter and the Penguin.

Retirement
Eventually, Bane's physical health deterioted and he couldn't survive a day without a daily dose of Venom. Literally a vegetable, Bane relocated to a private care estate where he was watched by a caretaker with a hidden agenda of his own.