Which supervillain from Avengers cannot be used in the movies?

According to CBR's Spinoff Online, Kang the Conqueror is one supervillain from the Avengers who can't be used in Marvel/Disney's own movies at the moment, because of some slapdash contracting agreements. In other words, for as long as there's Marvel movies, it's unlikely we'll see Kang in them any time soon.

But with the way they're allowing such terrible misuse of Captain America now back in comicdom, we probably shouldn't feel sorry for them.