When the movie starts, his newfound maturity is reflected in his conversations with Pepper Potts about family and a future, and we're privy to a man moving on and somewhat at peace. However, this tranquility is rocked with the arrival of the Black Order and the kidnapping of Doctor Strange, which quickly ropes the Armored Avenger into a rescue mission.
He boards the Q-Ship and realizes it's now or never; but there's no Cap and posse as backup (heck, he even kicks Spider-Man off to save the youngster a one-way ticket to doom and gloom), and certainly no Hulk to catch him if he falls. But as unprepared as he is, he embraces it -- alone. His blind heroism is evident in him not listening to Pepper over his comms-link, as she pleads with him to get off the ship. She knows, just as much as he does, that he's about to embark on a suicide mission.
Nonetheless, Stark jumps headfirst into this challenge, to save a man he just met and also, for something he's only now understanding, the Time Stone. But with the deck stacked against him, he eventually finds a partner in Spidey to take on Ebony Maw, and here, we see him acting as a team player once more (thankfully). Most importantly, he's living up to expectations as someone ready and willing to sacrifice anything and everything, which builds to a one-on-one slugfest against Thanos.
At this point, Stark, with his gadgets broken and armor pummeled, is basically a very brave man fighting a godlike entity. Yet he persists, even with a planet being hurled at him; that is until Thanos actually stabs him and leaves him on the brink of death. Eventually, Strange bargains for Stark's life, gifting the villain the Time Stone as part of some mysterious end-game, leaving Stark well in disbelief. As Thanos goes on to execute his mission, with Stark stranded on Titan watching his allies perish, the weight of trying to save the universe finally breaks him.
When it's time for Spidey, the young hero he views as a protege, to die, Stark cradles him in an emotional scene that sums up the guilt of his failures. It's also one of Stark's most human moments, because amid all this grief, he simply has no solutions whatsoever as to what's unfolding. But despite this defeat, it's hard not to recognize a man who put the ghosts of past to bed, who laid his life down on the line -- as a soldier, husband and now, father figure -- and more so, as a man who, while he may not be the hero we like, well, he's very much the hero we deserve. It's a pity it just wasn't enough to stop the Mad Titan -- yet.
Directed by Joe and Anthony Russo, Avengers: Infinity War stars Robert Downey Jr., Chris Evans, Chris Hemsworth, Mark Ruffalo, Jeremy Renner, Scarlett Johansson, Paul Bettany, Anthony Mackie, Paul Rudd, Elizabeth Olsen, Tom Holland, Benedict Cumberbatch, Chadwick Boseman, Chris Pratt, Zoe Saldana, Dave Bautista, Bradley Cooper, Vin Diesel, Tom Hiddleston and Josh Brolin.