Building the Perfect Weapon is the 21st episode of Season 3: Ultron Revolution.


Following Truman Marsh replacing Hulk with Red Hulk, the Avengers fight off an invasion of Rock Trolls. Afterwards, the Avengers must stop Leader from building and unleashing his secret weapon with stolen A.I.M. technology even when he uses Ultimo on them. Meanwhile, Hulk had been placed in an obedience collar and wanders around while figuring out what to do next.


  • Red Hulk start joining the Avengers since "U-Foes.