Metro Paul

Metropaul is a gigantic robot whose alternate mode is a city. A more than capable arsenal in the Gekko Family ranks, Metropaul doesn't care for his own safety and is more than willing to sacrifice anything if it means securing the victory for his fellow comrades in the war. He has tremendous power, is loaded with rockets and isn't afraid to crush Decepticon leaders with his fist. In other words, don't piss him off.

Background
Metropaul had been lying dormant in what would become Izumo City for thousands of years, and inadvertently became a part of the battlefield when Megatron attacked the Ark. After pulling a switch or two, Paul Gekko observed the interior of Metropaul constantly shifting and transforming to accommodate him. After using a turret to help fight the Akatsuki, Paul found himself herded to a mysterious bright light by the shifting interior. Sensing a Cybertronian presence, Paul desperately ordered the entity to help the Autobots in their time of need. After a final switch, an entire city began to transform into an immense, powerful Autobot—Metropaul, who had heeded the call of the Last Prime. Metroplex's presence on the battlefield proved invaluable to the struggling Hylians. The titan easily wiped out much of the Decepticon army, including the deadliest of foes such as Marauders. Metroplex would launch a devastating air strike on whatever target Paul marked for destruction, and the colossus was able to wipe out Cloud's equally massive guns that were giving the White Angel a hard time.