After Gemerl and Eggman were defeated by Sonic, the power of the Chaos Emeralds caused Gemerl to go haywire and charge at Sonic, causing him to drop the Emeralds. Gemerl then used their power to transform into Ultimate Gemerl. Before leaving, he used one of his "arms" to grab Eggman and throw him into Sonic. When he recovered, Sonic then used the Chaos Emeralds to become Super Sonic and teamed up with Eggman to bring the out-of-control Gizoid down. What Sonic has to do is transfer his power into Eggman's Egg Mobile and throw him at Ultimate Gemerl's shielded "eye". Then Sonic has to dash and hit the "eye". At points, he will attack using rockets or extend his "arms" to fire laser beams to stop Eggman and Sonic. Also, he may extend an arm to fire some kind of beam that will stun Sonic if it hits him. Sometimes, he'll extend his arms and spin around slowly. At times, Ultimate Gemerl will extend two arms and fires a large beam, if dodged, one can use the time to charge the Egg Mobile and counter-attack.
At the end of the fight, Gemerl reverts back to his normal form and lands on a beach; Cream finds Gemerl once again. Heavily damaged and in need of repair, Tails repairs him albeit with a more friendlier personality and Gemerl quickly became friends with Cream.
An easier way to beat him is to have Super Sonic charge up the Egg Mobile for longer periods of time. The longer the Egg Mobile is charged and flung at the robot, the longer the eye will stay open; thus giving the player more time to damage the out of control Gizoid before the eye closes again.
The name "Nonaggression" is a reference to how Sonic and Dr. Eggman are working together instead of fighting each other.
Notably, the music that plays during the Nonagression stage is a remix of Emerl's theme and the theme of the Phi from Sonic Battle, also the song used in the arena Colosseum.