9. King Boo - Super Mario Sunshine
King Boo serves as the boss in the Sirena Beach level in Super Mario Sunshine. The fight takes place on a rotating roulette wheel, with the sinister spectre hovering in the centre. Boo will use a spinning slot machine to decide how to attack you. Depending on what the slots land on, Boo may shoot fruit, bubbles, enemies, or coins. When he spits out fruit, you need to grab a Pepper and chuck it back at him since, as we all know, ghosts cannot stand spicy food. While stunned, you can whack Boo with another fruit. Once you bashed this spherical spirit with three fruits, he'll be down for the count.
Fighting King Boo is frustrating because it's random when the slots spew out the Peppers. If you can't collect the Peppers, the crowned phantom cannot be harmed. It feels like the developers made the Peppers appear by chance as a lazy attempt to pad out the battle. Because they can only appear randomly, the fight can drag on far longer than it should.
Unsurprisingly, King Boo is detested by Speed Runners since the battle's length is out of the player's control.