8 X-Men Who Became Avengers
2. Beast
Henry McCoy, the X-Men's resident Beast, is one of the X-Men with the longest relationships with the Avengers - owing to his veteran status as a hero and his friendship with Wonder Man. The two have been on a number of adventures together, and Henry was even able to garner enough influence within the Avengers over the years to vouch for the reinstating of Wonder Man's membership after it was revoked.
Henry has been on a lot of major teams over the years, from the X-Men to the Inhumans, and even the Illuminati. Beast was initially brought on to the Avengers on a probationary basis only alongside cosmic hero Moondragon, after proving himself reliable he was given a full membership.
Through all of the friction that has happened over the years between the respective teams Henry has been a part of, he's found himself in the unique position of mediator and trusted counsel for all.