After the Avengers became outlaws of the government, Truman Marsh decide to make a new Avengers groups that would uphold the Inhuman resignation Act. He gathers and recruits Captain Marvel, Ms.Marvel, Vision, Ant-man, Red Hulk, Black Panther and Songbird to join the group.
After a disaster in Attilan which culminated in the destruction of the city, Truman Marsh (secretly Ultron disguised as a bureaucrat for the United States government) proposed that, for the common safety, all Inhumans should be registered. The Avengers disagreed with setting up such a system, and disassembled, severing their ties to the government. Because of this, Marsh created his own team of Avengers, called the Mighty Avengers.
Their first official mission was to stop Baron von Strucker and they did so, with the help of Black Widow and Iron Man. The Mighty Avengers criticized the original team, calling them "vigilantes" and "renegades". Later, Marsh sent them to intercept three runaway Inhumans--Haechi, Flint, and Iso. They were met by the Avengers, who had come to warn the teenagers of the raid. As a result, a fight between the two Avengers' teams broke up, Captain America got seriously injured and the main Avengers were arrested. The only member who avoided arrest was Black Widow, who combined forces with Medusa And Black Bolt to rescue the Avengers. After getting away, Inhumans all over the world started to lose control over their powers, because of the registration disks and it was at this moment that Ultron revealed himself as Truman Marsh.
The Mighty Avengers and the Avengers worked together against Ultron and his sentries army and, eventually, Ultron's physical form was defeated. Unfortunately, Ultron had managed to possessed Tony Stark's body, knowing the Avengers wouldn't harm him.
However, Doctor Strange arrived and cast a spell to save Stark's life and stop Ultron, but in doing so, Iron Man was left trapped in a state of limbo halfway between the Dark Dimension and the natural world. The Avengers vowed to honor their friend's sacrifice and find a way to bring him home, starting with setting a new Avengers base, since Avengers Tower had been destroyed 
- Captain Marvel
- Red Hulk
- Black Panther
- Songbird (defected on the main avengers team)
- Civil War, Part 2: The Mighty Avengers
- Civil War, Part 3: The Drums of War
- Civil War, Part 4: Avengers Revolution
Behind the Scenes
In the comics,