One thing the Marvel Cinematic Universe blatantly lacks is a real focal super-powered heroine. Ms. Marvel AKA Carol Danvers has been rumoured to potentially appear in this continuity for some time and would be a welcome addition to the Avengers roster, given that she is a hugely powerful character. In the comics, Danvers was originally an officer in the United States Air Force. She was caught in the explosion of a Kree device (the Kree being an alien race who it is now believed are confirmed to exist in the Marvel Cinematic Universe, given the blue alien we saw in Agents of S.H.I.E.L.D.) and resurfaced later with superhuman powers, including flight, superhuman strength, speed, stamina and durability, as well as the ability to project and absorb energy and she became a very prominent heroine both as a member of the Avengers and whilst flying solo. She appeared in the 2010 retelling of Infinity Gauntlet ("Avengers: Infinity Gauntlet") and would be of great assistance in the final battle with Thanos in a movie. Given the aforementioned Kree's inevitable appearance as regulars in the Marvel Cinematic Universe, she could easily be introduced in a movie or in Agents of S.H.I.E.L.D. and be drafted on to the Avengers roster.
