The Ultra-Mech Unlimited is an enemy in Ratchet & Clank, found in the robot factory on planet Quartu. They are giant blargian robots manufactured by Drek Industries, designed and mass-produced by the Ultra-Mech Scientist based on an enlargement device to transform conventional robots into massive killing machines.
The Ultra-Mech Unlimiteds did not appear in the 2016 re-imagined game.
The Ultra-Mech Scientist was originally contracted to re-engineer his enlarging machine to create heavily armed robots, unaware that Chairman Drek was involved. Upon learning of Drek's involvement, he aimed instead to destroy it. Instead, Clank offered to enlarge himself, and the Ultra-Mech scientist gave him the mission "Destroy the Ultra-Mechs". After destroying them, the Ultra-Mech scientist recalibrated the controls of the device to only allow for Clank's circuit pattern, presumably ending production on the Ultra-Mechs, and gave them an infobot with coordinates for Kalebo III.
Ultra-Mech Unlimiteds are huge, bipedal, yellow robots, with large jaws, and a single red eye. They have small arms with pincer hands, but have large shoulders, containing a spiked ball on their right shoulder for melee attacks, and a large rocket launcher on their left shoulder, firing slow rockets.
The Ultra-Mech Unlimiteds are only fought as Giant Clank, and despite their size, do not pose a significant threat. Their melee attacks will briefly interrupt Giant Clank, though their missiles deal little damage. The melee attacks are the only real threat, but any of Giant Clank's attacks can deal with them swiftly. Giant Clank's bomb attack will instantly destroy many at once.