The comic books treated the Red Hulk's identity as a big mystery, but Marvel Studios has never shied away from letting us know Harrison Ford's President Thaddeus "Thunderbolt" Ross would undergo a rage-fuelled transformation in Captain America: Brave New World.

How and why does Ross go from Commander in Chief to the thing he hates most?

The movie explains that Ross used Samuel Sterns as a scapegoat following the events of The Incredible Hulk, giving the world someone to blame for Abomination's rampage through Harlem. Sterns' intelligence increased greatly after his blood was contaminated by Gamma Radiation, and Ross continued exposing the scientist to it while he was in captivity.

It made Sterns even smarter - he can predict almost anything by seeing the probabilities - but left him horribly deformed. However, it also gave Ross someone who could provide him with the solution to any problem (all while...