He is an evil space pirate who is respnsible for mind-controlling the planets and for kidnapping Ristar's father. Ristar goes on a quest to restore peace to the planets and defeat Greedy.
On the final level, Ristar finally comes face to face with Greedy. He tries to banish Ristar in a black hole and zap him, but Ristar managed to take down Greedy with ten hits. Upon his defeat, Greedy was banished into a black hole along with his henchmen, Inonis and Uranim, and Ristar escaped before Greedy's castle was destroyed.
His final fate in the Japanese version reveals him stranded on a distant planet with his henchmen.