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.

Appearing in "Building the Perfect Weapon"

Featured Characters:

  • Avengers
    • Captain America (Steve Rogers)
    • Iron Man (Tony Stark)
    • Falcon (Sam Wilson)
    • Hawkeye (Clint Barton)
    • Black Widow (Natalia Romanova)
    • Thor
    • Red Hulk (Thunderbolt Ross)

Supporting Characters:

  • Friday
  • Hulk (Bruce Banner)


  • The Leader
    • Humanoids (First appearance)
  • A.I.M. (Advanced Idea Mechanics)
  • Ultimo (Destroyed)
  • Rock Trolls

Other Characters:

  • Truman Marsh (Secretly Ultron)


  • Humans
  • Asgardians
  • Rock Trolls