I made a similar thread in the DC forum for the DCEU, but I figured why not make one for the Marvel side. Its trickier here, though, since the MCU has been around longer than the DCEU and has used a lot more of Marvel's iconic villains. However, there are obviously some that haven't popped up yet.
Obviously, there are the ones that have been been restricted because of the fact that Fox owned the rights up until now. So: Dr. Doom, Annihulus, Galactus, Magneto, Apocalypse, Mystique, Mister Sinister, Mole Man...pretty much all Fantastic Four and/or X-Men villains. But what about the ones not tied to either of those franchises?
Let's start. For me, it'd have to be:
- Amora the Enchantress
- Veranke
- Super Skull (that is, if we don't count him as an FF villain)
- Spidey's rogues: i.e. Green Goblin, Doc Ock, Kraven, Hobgoblin, Venom, etc. (though a few of those may still be off-limits?)
- The Leader (we saw Sam Sterns in Incredible Hulk and they even teased him becoming Leader, but they never did a sequel)
- Kang the Conqueror
- Taskmaster
- Mephisto
- High Evolutionary
- Sin
- Korvac
- Blackheart
- Immortus
- U-Foes
- Red Hulk
That's...all I can think of for right now.