Tony Stark is a bit surprised that Thanos knows him in Avengers: Infinity War when the two characters meet on Titan, and the connection between them is never explicitly explained for the viewer. But the link between the two characters is one of the most cohesive threads that runs through the entire Marvel cinematic universe.
“You’re not the only one cursed with knowledge,” Thanos tells Iron Man before their climactic brawl. And that knowledge — that everything is in danger and extraordinary individuals must take responsibility for making it better — is what makes the two characters so similar.
Iron Man’s mission
Tony Stark didn’t know Thanos by name, but since the beginning of the series, Iron Man has been aware that something, somewhere, would threaten Earth. Stark became a superhero because he felt responsible for the planet after his family became rich and powerful through the sales of weapons. He nearly killed himself to save New York in the first Avengers movie, and that act caused him significant mental pain.
Stark was haunted by the idea that the threats were only going to get worse until they overwhelmed the Avengers. This obsession is what caused him to unknowingly create Ultron, and ultimately Vision. Stark’s acceptance of the Sokovia Accords stems, at least in part, from the idea that this was a burden he should put down, or at least let others in the government shoulder some of the weight.
So many of the Avengers’ problems stem from Stark wrestling with having what feels like the literal weight of the world on his shoulders. Even Stark’s relationship with Peter Parker is driven by a sense of responsibility, which is why Spider-Man’s ultimate “death” hit Stark so hard.
Of course Thanos knows him. Both knew that something had to be done, and through the entire series they both felt that they were the only people who could do it. They just moved in opposite directions.
“I think [Thanos] has the most specific connection to Tony because Tony is a futurist, and he has predicted a threat like Thanos,” Infinity War director Joe Russo said in an interview back in April of this year. “It’s lived in his brain even though he couldn’t name it. Tony is the most desperately driven, down to the core, to react against something like Thanos ... I think this is intrinsic to Tony’s psychology, and because Tony started it all with Iron Man, he has a special connection to the threat that’s facing him.”
Stark may be the one person who can stop Thanos from fulfilling his goal, and Thanos finally allows Iron Man to put a face to the dread and fear he’s been feeling most of his adult life — that’s why the battles between the two characters feel so brutal and strangely personal. They both believe they have been chosen, in some way, to save everyone. And they are each other’s biggest obstacles to achieving that goal.
“Once [Thanos] disposes of his armor, he almost becomes a holy warrior where he doesn’t spend a lot of his energy intentionally trying to murder people unless they are, in some way, a threat to his agenda,” Joe Russo says in the director’s commentary. “Almost no one ends up being a threat to the agenda except for Tony, who I think he feels has a sort of existential connection to Thanos.”
Thanos is done with Stark once he impales the Avenger and it looks as if the armor won’t regenerate. “You have my respect, Stark,” Thanos tells him, with a voice that sounds regretful. “When I’m done half of humanity will still be alive.”
It’s not a comforting message, but it’s meant to help Stark feel like his efforts weren’t in vain. Thanos isn’t a threat to humanity’s survival, he just wants to kill half of everyone. Invasion or genocide aren’t part of his plans. As ultimate destruction goes, it’s not the absolute worst one possible.
When Thanos tells Stark that he “hopes they remember you,” he’s talking about himself as much as he’s talking about Iron Man. They both wanted to do the same thing: To save people, to make everything better. If Iron Man is remembered fondly, maybe Thanos will be as well.