Grizlock was an enemy of Supreme. When Supreme vanished for 47 years, Grizlock took the opporunity to kill various friends of Supreme: running over Billy Nelson (a Jimmy Olsen stand-in), chopping off the head of Junior Supreme Squad members and some unknown fate to Supreme's girlfriend Louise (a Lois Lane stand-in). He was captured by G.A.T.E. Industries. They had him work for them although he lived in a prision cell-like room. What he actually does is unknown. When Supreme came back, he attempted to kill Grizlock, but was stopped by Heavy Mettle and G.A.T.E. CEO Jason Temple.
Powers and Abilities
If Grizlock has any superpowers, he never shows them. G.A.T.E. staff constantly state he is a valuable resource. No explanation is given why he is so valuable.