Detective Comics, Vol. 1

Harvey Kent (not a typo; last name changed later) was a great D.A., and known for his handsome features. A criminal named Marconi is put on trial by him, and when Kent reveals damning evidence in the form of a two headed coin, Marconi snaps. The mobster throws acid at the D.A. Batman isn't fast enough to deflect the throw completely, and only half of Kent's face is burned. Horribly disfigured, he looks into plastic surgery, but the only doctor who might help him (Dr. Ekhart) is currently in a Nazi concentration camp. Kent snaps, seeing himself as two people. After scratching up one side of Marconi's coin, he then uses it to help him decide between the good and evil within him, alternating between committing crimes and committing acts of the highest charity.