It’s unlikely that we’ll ever see a film based on the 1974 team-up of The Avengers, the Fantastic Four and The Inhumans, but one can dream of the possibilities.
Crystal
Before the Kree on Marvel's Agents of S.H.I.E.L.D. and before the Inhumans there was simply Medusa, the scarlet female quarter of the villainous Frightful Four.