Avengers 1959 establishes there was a 1959 Avengers team lead by Nick Fury, consisting of Dominic Fortune, Kraven the Hunter, Namora, Sabretooth, Silver Sable, and Ulysses Bloodstone.
Avengers: Earth's Mightiest Heroes (2005) adds behind the scenes details to the early The Avengers stories that did not exist then, such as Captain America visiting the Vietnam War Memorial, or showing villains dealing out more destruction than in the original stories, such as the Black Knight Nathan Garrett firing on civilians instead of just spraying Adhesive X.
The Crossing was reviled for many reasons, chief among them being it tried to state that Iron Man was really a Manchurian Agent for Kang the Conqueror since the Avengers first fought him (which heavily derailed Iron Man's character) and that the various mental issues Hank Pym suffered over the years were really an earlier attempt to turn him into one before Kang moved onto Tony. The Crossing was so reviled that many elements of Avengers Forever were itself a retcon towards it. It was revealed that the mastermind behind the story was actually Immortus disguised as Kang in an off-the-rails attempt to distract the Avengers from preparing for Onslaught, which was one part of a possible timeline where humanity conquers the stars. Tony Stark was never Brainwashed since the Avengers first fought Kang, but was being controlled by Immortus since Operation: Galactic Storm. It was said to be brainwashed Fantastic Racism that went completely overboard and that Immortus lied through his teeth when he said he was the cause of Hank's issues. Various faces who turned evil throughout the story turned out to be Space Phantoms.
In Fantastic Four Annual #4, the Human Torch android was revived by the Mad Thinker to fight the Fantastic Four. In Avengers #133, Ultron reconstructed the Human Torch android to become the basis for the Vision. Avengers Forever reveals Immortus created and merged two timelines where both events happened. The Human Torch android body was still around, while the Vision still remained active as an Avenger. This allowed the Human Torch android and the Vision to both exist without causing a time paradox. The Human Torch android was revived later.
Avengers: The Origin gives a modern, broad strokes origin for the Avengers, replacing the Teen Brigade's ham radios with flatscreen computers.
In Scott Lang's first appearance, his daughter Cassie suffered from a congenital heart defect. To save her life, Scott stole Hank Pym's Ant-Man equipment and Pym Particles, which he used to rescue Doctor Sondheim, the only doctor able to cure Cassie's condition, from Cross Technological Enterprises. Scott's wife, and Cassie's mother, never appeared or was mentioned, with it being implied that Scott was raising Cassie alone. In fact, when Scott was in prison, his sister Ruth Lang and her boyfriend Carl were the ones that took care of Cassie, and have since disappeared. Then in Avengers Vol 3 #62, Scott's ex-wife Peggy Rae appears when she obtains a court ruling limiting Scott's time with Cassie to supervised visits for one month. Despite the fact that before that issue, Cassie was under his custody with no problems.
Mighty Avengers vol 2 #12 establishes there was a Mighty Avengers team during the 1970's.
◊. They've attempted to retcon this story twice. Once, by having everyone on the Avengers forced to play along in order to help Hank cope
