There have been four Avengers films in the MCU thus far but only Avengers: Endgame justifies the team's collective name. It's been several years since Earth's Mightiest Heroes was properly established in the universe. Since then, they've worked together in multiple missions to ensure the safety of Earth and have also changed roster a couple of times. As the Marvel Studios franchise grew more popular over the years, so did its premiere superhero team with the Avengers becoming a household name. That said, when really thinking about it, their name didn't make sense until later on.
Loki's (Tom Hiddleston) arrival on Earth in The Avengers to wreak havoc was the final push for Nick Fury (Samuel L. Jackson) to finally assemble the Earth's Mightiest Heroes as an attempt to contain the God of Mischief. Backed by a Chitauri army loaned from Thanos, not to mention both the Space and Mind Stones, the former director of SHIELD had no choice but to work on the Avengers Initiative that he initially hatched back in 1995. Bringing in the team to work together or at the very least, even want to partake in the mission was no easy feat, but with a clear and imminent threat, Iron Man (Robert Downey Jr.), Hulk (Mark Ruffalo), Thor (Chris Hemsworth), Black Widow (Scarlett Johansson), Hawkeye (Jeremy Renner), and Captain America (Chris Evans) set aside their differences for a common goal.
After The Avengers, Earth's Mightiest Heroes continued to function in varying degrees. The roster was officially expanded in Avengers: Age of Ultron with the addition of War Machine (Don Cheadle), Falcon (Anthony Mackie), Scarlet Witch (Elizabeth Olsen), and Vision (Paul Bettany). However, due to the falling out of Tony Stark and Steve Rogers in Captain America: Civil War, the team was defunct when Thanos (Josh Brolin) made the move against Earth in Avengers: Infinity War. By Endgame, the surviving heroes from the snap, including all six original banded back together for one final mission. Captain Marvel revealed the origins of the name — it was inspired by Carol Danvers' (Brie Larson) call sign as a Navy pilot. As nifty of a connection this is, it just really didn't make sense until Endgame.
As the name suggests, the Avengers' main function should be to exact retribution; the problem is until Thanos won at the end of Infinity War, the heroes didn't really have anything to avenge for. In The Avengers, the original six finally put their heads together on the heels of Phil Coulson's (Clark Gregg) death — this fit with their collective title as it made it look like they're avenging for his death. However, on top of Fury and Coulson conniving to fake the tragedy, this really has nothing to do with the bigger task at hand. Whether or not Coulson died, the original heroes would have to eventually team, otherwise, Loki would've succeeded in taking over Earth. Age of Ultron further proved this issue since the heroes were coming on a high when the new threat came around; it didn't help that Ultron was created by Tony and Bruce. Leading to Infinity War, there's really nothing going except for the break-up of the Avengers. For two years they didn't have any big mission so they stayed separated from each other, although Iron Man had been anticipating a new threat coming. The heroes fought gallantly despite not having a cohesive plan which ultimately led to their first-ever real defeat, this also finally gave them the chance to live up to their name.
It might have taken a while before the Avengers became worthy of their collective name, but the wait was worth it. Seeing the heroes at their lowest point only to eventually reconvene and ultimately win in Avengers: Endgame was satisfying for various different reasons. Granted that there were some personal differences among the heroes, particularly the first six Earth's Mightiest Heroes, but when push comes to shove, each one of them was committed to protecting Earth.
