When Thanos snaps the fingers of the completed Infinity Gauntlet in Avengers: Infinity War, he is transported to a Netherworld, where he sees the child Gamora. She asks him whether he accomplished his mission, and with a weary sense of triumph he states that he did. She then asks him what did it cost him, and now with a weary sense of sorrow, Thanos responds, “Everything.” But what ultimately divides Captain America and Iron Man is their mutual unwillingness to…