Guilty was the guardian of the Death Queen Island. He, different from the majority of villains, don't fight with the heroes. He just is a bad guy.
Guilty, in anime, was brainwashed in the Sanctuary and because this, forgot all his feelings, and his daughter, Esmeralda. In the manga, Guilty is naturally bad, and Esmeralda is not your daughter, but, a slaver of a habitant of the island.
He has serves in the anime with similar mask.
Guilty x Ikki
Guilty has taught Ikki to forget your good feelings, like him; according Guilty, the hatred is essential to win a fight. Ikki, initially refused this philosophy, but, when the Guilty attack hits, and kills Esmeralda, Ikki (that lived a Hell in the Island) becames a Demon Man, and kill Guilty. Before his death, Guilty says to Ikki where is the Phoenix Armor, and reveals Mitsumasa Kido is the Ikki's father.