Avengers Unleashed is a comic book taking place on Earth-606. After a time-traveling terrorist named Rajita Kang attacks, several heroes arrive on the scene to stop him, and form the Avengers.
Vol. 1 - Assemble
Plot: When a time-traveling terrorist from the future name Rajita Kang attacks, Spider-Man, Wolverine, Captain America, Thor, Hulk, Cyclops, Havok, Storm, Marvel Girl, Invisible Woman, and The Thing arrive on the scene. They fight off Kang, who manages to get away afterwards. When they decide to become a team, only Hulk, Thor, Captain America, Wolverine, Havok, and Storm stay, while the others go back to their normal, every-day lives.
Introduced: Spider-Man, Captain America, Thor, Hulk, Cyclops, Havok, Storm, Marvel Girl, Invisible Woman, The Thing, General Ross, Rajita Kang (Based On Kang The Conqueror), Nick Fury, Leonard Samson
Villains: Rajita Kang
Major Locations: New York, S.H.I.E.L.D. Helli-Carrier, Baxter Building, Midtown High, Oscorp, The I.N.S.T.I.T.U.T.E., Asgard
Vol. 2 - S.H.I.E.L.D.
Plot: S.H.I.E.L.D. is suspicious about The Avengers, and send Iron Man to see what's going on. It turns out that there's a race of shape-shifting robots made by HYDRA called Skrulls, and S.H.I.E.L.D. thinks one might have infiltrated the Avengers. When the Skrulls really do attack, Iron Man joins the Avengers to defeat them.
Introduced: Iron Man, Maria Hill, HYDRA, Madame Hydra, The Skrulls
Villains: HYDRA, Madame Hydra, The Skrulls
Major Locations: HYDRA HQ, Avengers Mansion, S.H.I.E.L.D. Helli-Carrier
Vol. 3 - Big Time
Plot: The Avengers are now iconic heroes, but they still aren't safe. When Hank Pym, a scientist from a branch of S.H.I.E.L.D. known as A.I.M. (which isn't a terrorist organization in this reality), creates a super-computer called U.L.T.R.O.N. 5, it is hacked by an unknown villain, and it traps the Avengers inside the Avengers Mansion, battling for there lives.
Introduced: Hank Pym, A.I.M., George Tarleton, Basil Sandhurst, U.L.T.R.O.N. 5 (Based On Ultron)
Villains: U.L.T.R.O.N. 5
Major Locations: S.H.I.E.L.D. Helli-Carrier, Avengers Mansion, A.I.M. Laboratories
Vol. 4 - Change of Plans
Plot: The Avengers' roster changes from Cap, Iron Man, Storm, Havok, Hulk, Wolverine, and Thor to Cap, Havok, Iron Man, Daredevil, Hulk, and... Hank Pym, who has decided to use technology to become the Ant-Man, a hero that can shrink in size. With the new roster, The Avengers are controversial for "kicking off" members and "replacing them" with new ones. FBI investigator Jane Van Dyne starts to follow the Avengers, and develops a relationship with Hank Pym, a.k.a. Ant-Man. However, in these dark times, The Avengers become a target for the mysterious assassin Taskmaster.
Introduced: Janet Van Dyne, Daredevil, Taskmaster
Major Locations: Avengers Mansion, New York
Vol. 5 - West Coast
Plot: Hawkeye and his team of pre-Avengers S.H.I.E.L.D. operatives (Black Widow, Mockingbird, Wonder Man, Tigra, and Falcon) return from the West Coast to warn S.H.I.E.L.D. of a group of terrorists, The Lethal Legion, who are heading for San Francisco. The "Avengers West Coast" and the Avengers team up to stop the terrorists and their leader, Tiger Shark.
Introduced: Avengers West Coast (Black Widow, Mockingbird, Wonder Man, Tigra, Falcon), Lethal Legion (Tiger Shark, Moonstone, Radioactive Man, Tomorrow Man, Scalphunter)
Villains: Lethal Legion
Major Locations: San Francisco, Avengers Mansion, Jenkins Laboratories
Vol. 6 - Avengers Disassembled
Plot: The last main arc of this series before it went on to New Avengers Unleashed. In this arc, a man named Franklin Hall becomes the new director of S.H.I.E.L.D., and he disbands the Avengers West Coast to form a new team of S.H.I.E.L.D. superheroes, the Dark Avengers. Secretly, Franklin Hall works for H.Y.D.R.A. and wants Captain America destroyed. Franklin eventually gets his hands on a specially designed Iron Man suit known as the "Graviton" suit, and becoming Graviton he leads the Dark Avengers during an attack on Avengers Mansion, in which the Avengers defeat the Dark Avengers.
Introduced: Graviton, Dark Avengers
Villains: Graviton, Dark Avengers (Crimson Dynamo/Dark Iron Man, Taskmaster/Dark Daredevil, Rulk (Red Hulk)/Dark Hulk, and Shocker/Dark Havok)