Wilde Norton's family was victims that the Joker had ever killed. Driven nuts by the incident, he started calling himself "Wild" and went after the Joker to kill him. He failed and was imprisoned in Arkham Asylum for the Criminally Insane. After the Gotham earthquake, the inmates of Arkham took control of the asylum at which time the Joker brutally murdered Wild.
Wild Has Not Appeared In Any Other Form Of Batman Media