-The Joker in his first appearance (Batman #1)
Not much is known about Jack Napier's early life besides that he had an abusive father, his mother died when he was 3 years old, and he got married at 24 years old.
Jack Napier was trying to be a good comedian, but nobody laughed at his jokes. He had a wife and himself to support and he couldn't get any money so he became a criminal. Red Hood to be exact. One day his wife died in a car crash. This pushed him over the limit and made it impossible for him to stop being a criminal. One night he planned out a heist on Ace Gotham Chemical Plants, but his plan was foiled by Batman. Batman headed towards Jack and he was so scared he jumped over the edge and fell in a vat of chemicals. He came out with his skin bleached white, hair green and had black eyes with white pupils. Seeing his appearance made him criminaly insane and he became The Joker.