Shadow Kingfin

Shadow Kingfin is the boss of the Shark Exhibit of the Haunted Aquarium and is the supposed king of all Bonefin. After being defeated, he gives the key to the fourth mansion and is seen as Ultimate Shadow Kingfin in the Palace of Shadow.

Shadow Kingfin
Shadow Kingfin is Kingfin possessed by the Shadow Queen and ordered to stop Luigi from advancing any farther. After being defeated, he gives Luigi the key to the fourth mansion.

Ultimate Shaodw Kingfin
Ultimate Shadow Kingfin is Shadow Kingfin powered up by the Shadow Queen to fight alongside Shadow Doopliss and the Shadow Koopalings who are also in ultimate forms. After being defeated, he opens the door that leads to the Ultimate Shadow Koopalings and thanks Luigi for freeing him from the Shadow Queen's control. He is not seen anymore after that except for in the minigame "Kingfin's Dark Reign."