SPOILER WARNING: This section may contain major plot and/or ending details. Proceed at your own discretion.
After discovering the severely weakened Anguirus, the CKR plans to use Kiryu and take him to a Russian facility. Meanwhile in Boston, Godzilla finds himself surrounded by multiple MechaGodzilla units which attack him with their finger missiles. Godzilla responds by hitting one of the robots with his tail, while another blasts Godzilla's neck with its finger missiles. Godzilla attempts to blast it with his atomic breath, but another MechaGodzilla hits Godzilla's face, causing his atomic breath to miss. Godzilla bites one of the MechaGodzillas' hands, but is injured when it fires its finger missiles in Godzilla’s mouth. Meanwhile, the U.S. Senator tells Dyachenko to finish Godzilla in Boston, but Dyachenko insists he wants to see Godzilla suffer with his own eyes. Before the Senator can protest, he is knocked unconscious by Minette and Mallory and taken away. After shedding his human disguise, Rhizon is informed by one of his underlings that Kiryu and Anguirus are heading to Russia, so he orders two MechaGodzilla units to blast them out of the sky, causing the CKR team alongside Kiryu and Anguirus to crash somewhere in Siberia. Back in Boston, the four remaining MechaGodzilla units activate their force fields against Godzilla. At first, the tactic seems successful when Godzilla tries blasting the shields and physically attacking them with no luck, but he unleashes his nuclear pulse which destroys the MechaGodzillas’ force fields. Godzilla then destroys one of the MechaGodzillas by stomping it into the ground and blasting the machine with his atomic breath. He then uses its arm to smack another MechaGodzilla. Another tries blasting Godzilla with its eye beams, but Godzilla fires his atomic breath, causing the beams to lock. Godzilla's atomic breath overcomes MechaGodzilla's eye beams, and the robot's head is blasted off. Another MechaGodzilla tries to attack Godzilla from behind, but fails to do so as Godzilla spots the MechaGodzilla and quickly destroys it. As the last two MechaGodzilla units get up, one of them headless, Godzilla tries blasting one of them, but is quickly stopped when a MechaGodzilla blasts Godzilla with its eye beams. Godzilla then throws the other remaining MechaGodzilla at it and slams both of them repeatedly with his tail. Godzilla appears victorious, when Mecha-King Ghidorah suddenly attacks Godzilla and captures him with his cables and machine hand.
The battle between Godzilla and the MechaGodzillas has many references to Godzilla's battles with MechaGodzilla in Godzilla vs. MechaGodzilla and Terror of MechaGodzilla. For instance, the MechaGodzillas at one point spin their heads to create forcefields that harm Godzilla when he tries to attack them. There is another instance where Godzilla's atomic breath locks with a MechaGodzilla's laser vision. Whenever a MechaGodzilla's head is removed, a lightbulb-type structure capable of firing a laser can be seen in its place.