The Avengers are a superhero team within Marvel Comics that is as established as the ‘Marvel’ brand itself, but while the Avengers are a flagship team now, it wasn’t always–and Captain America nearly destroyed the Earth’s Mightiest Heroes with one addiction.
Steve Rogers aka Captain America became the Super Soldier fans know and love today after he was subjected to experimental testing by the U.S. government resulting in Rogers becoming a full-blown superhero. While he was designed to be the greatest weapon for the Allied Forces in World War II, he was presumed dead after he and his sidekick, Bucky, took down a Nazi warplane near the end of the war. However, he was simply frozen in a block of ice and was later discovered by the Avengers and joined the team. Rather than taking a much-needed rest, Rogers couldn’t wait to get back into the action with his fellow superheroes—so much so that even being a hero on the Avengers soon wasn’t enough for him.
In Avengers #19 by Stan Lee and Don Heck, Captain America is feeling discouraged as he sent a letter to Nick Fury asking to join his special forces team within SHIELD, but hasn’t heard back. At this point on the Avengers team, there are no founding members left as Iron Man, Ant-Man, Wasp, and Thor have decided to take an indefinite leave of absence. So, Captain America is the leader over the new members: Hawkeye, Scarlet Witch and Quicksilver—all of whom began their careers as villains and are totally new to the superhero scene. Basically, Captain America is the only thing holding this team together but he feels underappreciated and underutilized. In this issue, it had been some time since the last Avengers-level threat, and Captain America wanted to be used as a legitimate soldier once again rather than as a glorified babysitter to a team of reformed villains.
After weeks of hearing nothing from Nick Fury about his status as a SHIELD agent, Captain America finally gets a letter back that tells him to meet at a secure location to discuss next steps. Captain America is overjoyed at the prospect of leaving the Avengers and being thrown into an environment of non-stop action as SHIELD constantly has missions pending. On the flipside, the Avengers mostly sit around and wait for catastrophe that is way too few and far between for Captain America’s liking. Rogers can’t stand inaction and needs the rush of constant adrenaline-pumping missions so much so that it's safe to say that he was addicted to it—and that addiction nearly destroyed the Avengers before the team really had a chance to take off.
While Captain America may have felt underutilized while leading this ragtag version of the Avengers, he single-handedly saved the greatest superhero team in Marvel Comics history. If Captain America left the Avengers to become a SHIELD agent, the only members left would have been Hawkeye, Quicksilver, and Scarlet Witch, and that is not a substantial line-up (especially given the fact that they all had very recently been acting as villains at that time). Captain America almost let his need for constant action destroy the Avengers—nearly reshaping the entirety of Marvel Comics history because of his addiction to never ending violence.