10 Most Powerful Avengers Ever
7. Scarlet Witch
Though she may be more associated with the X-Men and other Mutant organizations, Wanda Maximoff, aka the Scarlet Witch, joined up with the Avengers early on in the team's history. She came onto the team (with her brother) all the way back in The Avengers #16 in 1965.
That's early enough to call her a starting member seeing as she came onto the team when the original roster all but abandoned it. Only Captain America remained to rebuild the team from the ground-up, and he did so with the help of the Scarlet Witch.
While she isn't the only Mutant to have an Avengers I.D. Card, she is the most powerful one to join up with the team. In terms of power, she started out somewhat ill-defined and weak compared to her later depictions. In the beginning, she had limited control of hex magic and could do some damage, but as her Mutant abilities evolved, she gained the ability to alter reality itself.
She unwittingly started the House of M crossover event that led to the removal of nearly all Mutants in the Marvel Universe. Ultimately, she became the catalyst for the Avengers vs. X-Men event, which led to the death of Charles Xavier.