In Paper Mario: Color Splash, what is the name of the final boss?

In Paper Mario: Color Splash, the final boss is Black Bowser.

Near the end of the adventure, Mario and Huey recover the six Big Paint Stars and learn what happened on Prism Island. Bowser had entered the Prisma Fountain intending to recolor his shell, but mixing the paints created toxic black paint. The substance covered and possessed him, transforming him into Black Bowser.

The final confrontation takes place at Black Bowser’s Castle, where Bowser is producing weaponized black paint in a factory. Mario battles him with painted cards and special attacks while Huey helps stop the factory’s operations. After Black Bowser is defeated, the castle begins to collapse and the black-paint threat is removed from the island.

The name can cause confusion because ordinary Bowser appears throughout the Mario series and is also present in Color Splash. Here, however, “Black Bowser” identifies the possessed, black-paint-covered form that serves as the game’s climactic opponent. Color Splash was released for the Wii U in 2016.