Marc Spector has been one of the most ferocious fighters in the Marvel Universe ever since his transformation into Moon Knight. And over the length of his superhero career, he has fought both against and alongside everyone from Blade to Captain America, serving as a part of several superhero teams.
While he rejected Black Panther's most recent offer to join the team, Moon Knight has had the distinction of serving with different incarnations of the Avengers, Earth's Mightiest Heroes. While not every squad of Avengers is created equally, Moon Knight has always made an impact on whatever team he joined.
West Coast Avengers
When the Avengers were lost in Ancient Egypt, they just so happened to arrive during the rule of Rama Tut, better known as Kang the Conqueror. After being sentenced during 1987's West Coast Avengers #21 by Steve Englehart and Al Milgrom, the team was prepared for their still-living burials in a temple to Khonshu only for Hawkeye to make contact with the ancient god Khonshu. He was unable to assist the heroes directly, but the deity was able to send Marc Spector a message in the present.
Moon Knight worked with Hank Pym and Firebird to save their allies and remained with the team for a short time afterwards. Marc eventually left the team alongside Tigra and Mockingbird when it came to light that the latter had allowed a villain to die instead of saving him in an act of revenge. This also led to Marc shying away from Khonshu's influence for a time.
Secret Avengers
Years later, Moon Knight would join Steve Rogers' team in 2010's Secret Avengers #1 by Ed Brubaker and Mike Deodato Jr. The titular force had been assembled following the end of Norman Osborn's reign as the head of the Avengers and the Fifty-State Initiative, and was comprised of the best black-ops soldiers and heroes that Cap could find.
As part of this team, Moon Knight took part in a mission to rescue Richard Ryder, aka Nova, from the possession of a dark force on Mars and assisted in a subsequent battle against the Secret Empire. It wouldn't be long, however, before Marc was pulled away.
Avengers vs. X-Men
While tensions between Marvel's two biggest teams began to boil over during 2012's Avengers vs. X-Men event, Marc Spector stepped into the center of the conflict in the pages of 2012's X-Men: Legacy #266 by Christos N. Gage and Rafa Sandoval. With the Phoenix Force on its way to Earth to take Hope Summers as its next host, the Avengers were preparing for the worst, while the X-Men hoped that the Phoenix would bring about the next generation of mutants. In the hopes of preventing any further mutants from joining in the fight against them, the Avengers sent Moon Knight, Falcon, and She-Hulk to the Jean Grey School for Higher Learning as a preemptive deterrent.
When Frenzy goads Moon Knight into attacking her by bringing up the sordid past he has kept hidden from his own team, students are caught in the crossfire, and all hell breaks loose on the academy grounds. Marc Spector's multiple personalities proved useful for a time in keeping Rogue off balance and unable to focus. But just like the rest of his team, he proved no match for the combined might of so many mutants fighting for the very existence of their species.