With Metal Sonic knocked out of the fight, the player transports to the another hall that leads to Fang the Sniper, who briefly makes an appearance. Presumably in the Atomic Destroyer to steal the final Chaos Emerald, which is now in Robotnik's possession, Fang turns and flees after catching sight of Robotnik's armored mech with pogo attachment, leaving the player to face the Doctor one-on-one.
The machine's defense is mediocre and Robotnik only has a linear pattern to bounce towards the player. The player can easily hit the mech many times, but the only thing the player should avoid is to get not crushed by the mecha. After ten hits, Robotnik quickly moves away to the next room, where doctor is waiting the player on his another vehicle to be encountered.