If Marvel and Universal didn't come to a deal with using The Hulk, who would Marvel have used in The Avengers?

Basically the title. At the time, there was an Ant-Man movie stuck in development hell, Fiege wanted to do Black Panther but got pushback from the other Marvel executive at the time.

Which Character do you think Marvel would have chosen? Maybe they don't even have a solo movie before The Avengers and are introduced in that movie.