Avengers: Endgame 

Robert Downey Jr.’s portrayal of Iron Man in the Marvel movies completely reshaped his career and set the tone for much of the rest of those movies. The climactic film, Avengers: Endgame sees our heroes, half of whom had been erased in the previous movie, face off in a final battle against the villain, Thanos. 

Josh Brolin’s Thanos is ready to erase half of existence for the second time, and cockily reiterates his “I am inevitable” line from Avengers: Infinity War. Downey was supposed to reply “And I am the guy in the suit,” but decided to instead say “And I…am… Iron Man,” making the ultimate callback to his original line from Iron Man that kicked off the whole Marvel Cinematic Universe.