Grrkek is a giant alien lizard who can kill millions and destroy planets who cares for nothing but destruction and misery.
Grrkek was sealed away long ago for his crimes against the galaxy, but was released by Coop when he was testing a new game, not knowing it was a containment cartridge. Coop fought Grrkek and then blasted him, but this only turned him into a cocoon and transformed him into a bigger and stronger form.
Grrkek was finally defeated when he got caught in a tidal wave which Coop caused and it shrunk him back down to size. He is now trapped in a "Love Those Lurps" game console cartridge, which greatly annoys him to no end.
Grrkek is very cruel, caring for nothing but destruction and misery.