Hulk
I think they will fight Hulk in the first half of the movie and gain him to fight against who ever else is the other villain in the second half of the movie.
And in that case it might as well be Loki, just like in the first Avengers comic.I think they will fight Hulk in the first half of the movie and gain him to fight against who ever else is the other villain in the second half of the movie.
I'd like a big, elaborate plot by the Masters of Evil (though maybe they shouldn't call themselves that) with Loki as the mastermind.
There's something very resonant about the Avengers being pit against their own creations. I say give us Ultron. Everything else is either too small (Red Skull? Doesn't Captain America beat him solo?)
And this guy< cleaned his clock!