Attack of the Final Boss! is the 10th episode of Metal Cardbot, and the first appearance of Heavy Iron and Wild Guardy.

Plot

Jun and his Metal Cardbots investigate the broken-off escape pod that was deflected in the final moments of S1E9, 0 Seconds to Destruction. Inside is a semi-truck trailer that the Metal Breath identifies as being owned by Heavy Iron, a ruthless outlaw from planet Machina. After the news reports an oil tanker explosion caused by a giant submerged entity off the coast, the group realizes Heavy Iron survived the crash and is travelling toward Mowtown to reclaim his trailer body.

To avoid civilian casualties, Jun has Mega Trucker tow the heavy trailer out to an abandoned construction site near a mountain tunnel. Before they can stow the trailer in the tunnel, Heavy Iron arrives in his truck vehicle mode. Jun uses Mega Ambler, Phoenix Fire, Shadow X, and Blue Cop to slow him down, but their attacks fail to stop him. As a last resort, Jun lures Heavy Iron into the tunnel and has Blue Cop collapse the tunnel with his Burst Shot. Before the group can celebrate, Heavy Iron breaks free out of the mountain and transforms into his colossal robot form. His Iron Cannon completely overpowers all of the Cardbots, and he demands that they kneel before him.

Just as defeat feels certain, a mysterious knight Metal Cardbot appears and attacks Heavy Iron, creating an opening for Blue Cop to strike back with a Megavolt Punch. Heavy Iron retreats with his trailer into the mountains, while the mysterious Cardbot vanishes before Jun can discover their identity.