“I have, but I won’t mention which one,” Baldwin revealed. “I don’t want to undo somebody because they hired someone else to do it. But they asked me to play a villain in one of these Marvel Comics movies. I wasn’t available, they wanted me to work a certain time. And because of my wife’s pregnancy, I had to turn down two films this summer that I wanted to do.”
Given that his wife is 6 months pregnant, the movies he could have been offered are The Amazing Spider-Man 2, Captain America: The Winter Soldier, X-Men: Days of Future Past, and Guardians of the Galaxy. Perhaps they were gonna bring him in as Carnage in the Spider-Man film. Man, Carnage is so needed.
SOURCE: Comic Book Movie