"To the victor go the spoils as well as the best theme song. Thunderfist is the biggest robot of all. It failed military testing (hence the missing arm) so Blast Corps took it off their hands. Thunderfist is immensely powerful but must be used with care. Press A to start a roll attack. Chaos ensues."
Powers and Stats
Tier: High 8-C
Origin: Blast Corps
Age: Unknown, possibly 5 years (the company Blast Corps existed five years before start of the game and Thunderfist was taken by Blast Corps from the military as a failed project)
Height: 20 meters
Weight: 200 tonnes
Classification: Blast Corps mech
Powers and Abilities: Superhuman Physical Characteristics
Attack Potency: Large Building level (Can easily destroy large buildings by colliding with them)
Speed: Superhuman running speed (50 mph) with Subsonic rolling speed (100 mph)
Lifting Strength: Unknown, likely at least Class K due to size and weight (Weighs 200 tonnes)
Striking Strength: Large Building Class (Casually destroys large buildings)
Durability: At least Large Building level (Easily destroys large buildings with no apparent issues) to possibly Small City level (Can survive a detonation capable of causing nuclear winter)
Stamina: High (Doesn't visibly tire or run low on fuel in gameplay)
Range: Close range / melee
Standard Equipment: None
Intelligence: Non-Sentient machine
Weaknesses: Missing one arm, though this never affects its ability to do its job. Does require a pilot
Feats: Cleared the path of a runaway nuke carrier by somersaulting through cities.
Notable Attacks/Techniques: Thunderfist can destroy buildings of various sizes by simply walking into them or somersaulting ("roll attack") into them. "The more roll attacks performed consecutively, the more powerful it gets."
Note: While the canon explanation for Thunderfist's missing arm is connected to failed military experiments, supposedly the real-life story is that there wasn't enough memory left to program the second arm into the game and the developers felt Thunderfist looked cool enough with just one arm.