Robert Downey Jr. did not merely put on the Iron Man suit; he practically became Marvel in human form. What began with Jon Favreau championing a risky casting choice became the beating heart of the Marvel Cinematic Universe. Downey anchored 10 films over 11 years, transforming Tony Stark from a comic-book character into a global cultural icon. His defining sacrifice in Avengers: Endgame.link { text-decoration: underline; font-weight: bold; text-…