Ghoul

Ghoul, a member of the third Jokerz gang. He is seen in the movie Batman Beyond: Return of the Joker, and an episode of Justice League Unlimited (The Once And Future Thing: Part Two.) Here's his biography:
He wears ragged clothing and has grey skin, numerous stitching/scar marks and skull-like features; possibly genetically altered his appearance to make himself look undead. His appearance vaguely mimics that of previous Batman nemesis Scarecrow and his voice and mannerisms are loosely based on Christopher Walken. A jaded young runaway from a wealthy home, Ghoul joined up with the Jokerz for kicks. He's heavily into techno-goth music and has adapted the horror look into his costume. Ghoul is never without his plastic Halloween pumpkin which he keeps filled with a number of monster-inspired weapons and tricks. Ghoul eventually returned with a spinning blade in his right arm which he can deploy or retract at will.