Ultimaton, also known as Weapon XV, is a supervillain in the Marvel Universe and enemy of the X-Men. Ultimaton first appeared in New X-Men #143 (August, 2003) and was created by Grant Morrison and Chris Bachalo.
Ultimaton was created to be the powerhouse of the Super-Sentinels, a team of mutant hunters conceived by John Sublime as a publicity stunt to make the extermination of mutants acceptable to the public. Fantomex and Huntsman were intended to be his teammates, but Huntsman had been destroyed and Fantomex had gone rogue.
Ultimaton was released from the World when the facilities were attacked by agents of Advanced Idea Mechanics, who wanted to recoup the technology Weapon Plus had stolen from them. Ultimaton wiped out the attackers and later fought Wolverine, Fantomex and Cyclops and escaped to the Super-Sentinels orbiting base, constructed in a remnant of Asteroid M. At this point, Ultimaton had begun to wonder about his purpose in life, questioning his fate of being a mutant-hunting killing machine.
Fantomex, Wolverine and Cyclops followed Ultimaton to the space station, where Fantomex and Cyclops fought Weapon Plus agents. Wolverine denied Ultimaton's claims that he could have been a painter before destroying the space station. In The New X-men #148, Wolverine later tells Jean about how he finished off Ultimaton right after the explosion, while it was contemplating the purpose of its own existence, and wasn't paying attention.