Tired of guerilla tactics, Kevin decided it was time he took the war directly to Fuse's lair. With the help of the Hero, he was able to collect some samples of the local Fusion Spawns, and absorbed their Fusion Matter, hoping to match Fuse's strength.
Unfortunately, Kevin's plan backfired, and Fuse gained control over him by means of the absorbed Fusion Matter. Under Fuse's control, Kevin tricked the Hero into attaching a device to Foster's Home in order to transfer Imaginary Energy to Fuse's lair in the Darklands for study. Fortunately, Dexter was able to uncover the plot, and was able to slow down the transfer and free Kevin from Fuse's control. Dexter was unable to stop the transfer completely, however, because doing so would prove fatal to the Imaginary Friends. Nonetheless, the transfer seems to have slackened after Billy got into Fusion Kevin's lair in Green Maw. Fuse continues to use Kevin by using car keys stolen from him to produce an army of Fusion counterparts that resemble eleven-year-old Kevin's giant alien form in Fuse's Lair.
- He was changed to his design from Ben 10: Alien Force Season 3.
- He is one of few characters that players are able to fight.
- His Fusion is on his mutated form instead of his human form.
- Fuse was still able to create Kevin's "11" Fusion counterpart with Kevin's which he got when he was eleven years old. Notably, his Diamondhead arm is a slate grey, while Fusion Tetrax has regular green fusion skin, despite being made of the same material.