Croc (image credit goes to Grimm)
Croc is a villain who appears in I,The Knight. No one knows what the criminal known as Croc's real name is. All they know is that he's a huge monster with a rare mutated skin condition that makes his skin look like green scales. Croc grew to resent the human race for their prejudice against him. One day he filed his teeth into fangs and started a career in crime. At one point Croc kidnapped Jim Gordon's daughter Barbara and held her for ransom. Batman went into the sewers and did battle with and defeated Croc. Batman took Croc to prison where Croc swore revenge against Batman!
Croc later with the help of Riddler, escaped Arkham Asylum and teamed up with Riddler in order to have vengeance on Batman. But he and Riddler did not make the best team and were easily taken back to Arkham.