Avengers

"'We’re putting a team together. A response team for global threats. You don’t work for us. We just tell you where you can be to help, and hope to God that you show up.' (Xavier Bronze's SI, Kindred Minds)"The Avengers are a team of SHIELD-sanctioned vigilantes, gathered by Nick Fury and led by Phil Coulson. All the members are either highly trained or superhuman. The team fights threats to global security, such as the Ten Rings.

History
The Avengers Initiative was initially created by Nick Fury as a potential response to a superhuman such as Superman going rogue. The objective was to gather a list of extraordinary individuals, such that no one of them could stand against the rest. The list was compiled, but the World Security Council didn't permit Fury to move forward with contacting any of the candidates.

In 2011, the project was reactivated in earnest, under the guiding hand of Phil Coulson. A mysterious consultant named Xavier Bronze advised them on the final lineup, and several people were contacted and offered a place on the team. A party was organized, where many of the members met each other.

The Avengers' early missions were against the Ten Rings organization. When one of their own was abducted by the organization, they hunted down every base they could find. And after she was rescued, they took down AIM, who they learned had been behind many of the Ten Rings operations they had been fighting.

Members
Phil Coulson, "The Thunderer"

A loyal agent of SHIELD, empowered by the Asgardian artifact Mjolnir with the divine might of the God of Thunder, Thor. The team leader.

Clint Barton, "Hawkeye"

A SHIELD operative. The greatest archer on earth.

Natasha Romanoff, "Black Widow"

A former Soviet assassin, recruited into SHIELD by Clint Barton.

Xavier Bronze's SI, "Avatar"

A reincarnating spirit warrior from another universe with elemental powers. Became a SHIELD consultant and informant.

James Rhodes, "War Machine"

A loyal military officer and long-time friend of Tony Stark. He stole one of Stark's armors.

Clark Kent, "Superman"

An alien refugee from a dead world, raised on earth from a young age.

John Constantine, "Hellblazer"

A self-proclaimed Master of the Dark Arts. A magician who specializes in the demonic.

Invited
Melinda May, "Cavalry"

A former SHIELD operative, undyingly loyal to Phil Coulson. She rejected the offer due to trauma from a past mission.

Matt Murdock, "Daredevil"

A blind man, trained by a ninja named Stick to fight in an ancient war. Rejected the offer due to past experiences with Stick.

Jessica Jones, "Jewel"

A super-strong orphan, adopted into a loveless family. Rejected the offer because she wasn't certain enough to accept it.

Bruce Banner

A pioneering scientist in the fields of radiology and biochemistry. Put off accepting outright in order to give it a "trial period".

The Hulk

An entity created by gamma radiation with super-strength and regenerative abilities. Hasn't accepted yet due to still-building trust.

Considered
Emil Blonsky, "Abomination"

Considered by the World Security Council. Efforts to gain access to him were sabotaged by Phil Coulson.

Tony Stark, "Iron Man"

Considered by SHIELD. Xavier Bronze's SI convinced them against inviting him, suggesting James Rhodes as an alternative.

Oliver Queen, "Arrow"

Considered by Xavier Bronze's SI. Currently unavailable.

Kara Danvers, "Supergirl"

Considered by Xavier Bronze's SI. Decided against in order to allow her a more normal life, and to respect Superman's wishes.

See Also:
Avengers, on Marvel Cinematic Universe Wiki