Waylon Jones (Earth-4678)

Waylon Jones was abandoned to his abusive and alcoholic aunt and abused and bullied his entire life due to his appearance, the result of a the atavism disorder he was born with. Waylon Jones embraced his animal instincts and violently murdered and devoured his aunt after he finally reached his breaking point. Joining a traveling circus and adopting the stage name of Killer Croc, Jones bonded with his fellow carnival workers and felt like he had a family for the first time.

That came to a tragic end, however, when vicious audience members in Gotham City destroyed the carnival and killed all whom Jones had felt affection for. Seeking revenge on all humanity for their crimes, Croc began to devour countless individuals to survive, and became a monster in both body and spirit. Driven by hatred and a lust for blood, Croc regularly worked with Gotham's various mob organizations as a brutal and cannibalistic hit-man to satisfy his appetite for violence and money.

Source

 * https://arkhamcity.fandom.com/wiki/Killer_Croc