The title Avengers: Endgame isn't just a callback back to a quote from Avengers: Infinity War; it actually goes back even further to Avengers: Age of Ultron. While the most famous instance of a character saying "endgame" is arguably when Doctor Strange said "We're in the endgame now" before he faded to dust thanks to Thanos' finger snap (now officially known as The Decimation), it was actually the Avenger he said it to, Tony Stark, who first uttered the word in reference to the cosmic calamities facing Earth's Mightiest Heroes. As such, Endgame becomes a tidy way for Marvel to narratively tie every Avengers film together.
After months of fan theories, the Avengers: Endgame trailer finally ended the debate of what the title of Avengers 4 would be. Now that we know it's Endgame, the next step is trying to decipher what hidden meaning the title holds. The obvious reference to Doctor Strange's quote in Infinity War nicely positions Endgame as its sequel, with the word containing more than one meaning. "Endgame" foretells whatever the Avengers' plan will be as they try to right the universe from the damage inflicted by Thanos; it also plays into Avengers 4 being the conclusion of the 22-film cycle that began with 2008's Iron Man, opening the door to Marvel's Phase 4 and the future of the MCU. But what can fans learn from when Tony Stark uttered "endgame" in Age of Ultron?
Why Tony Stark Teased "Endgame" In Avengers: Age of Ultron
As he watched Doctor Strange fade to dust, Tony Stark was probably too traumatized to remember that it was he, not the wizard, who said "endgame" first in Age of Ultron. In Joss Whedon's 2015 sequel, Stark found himself rebuffing the Avengers' blame for Ultron's surprise attack on Avengers Tower. Iron Man reminded them of when he saved the world by flying S.H.I.E.L.D.'s nuclear missile through the wormhole over Manhattan in The Avengers, where he then saw the massive Chitauri invasion fleet and nearly died in the process. Tony argued to his fellow Avengers: "We're the Avengers. We can bust arms dealers all the livelong day, but that up there... that's the endgame."
The endgame Iron Man is referring to is aliens of such overwhelming power that even the Avengers can't stop them. Since Stark's near-death experience and his glimpse of the extraterrestrials threatening the Earth, he has never been the same. Tony's reason for originally building Ultron was to create "a suit of armor around the world" that would protect the planet from aliens. Stark's need to protect Earth with Ultron was exacerbated by the dream given to him by Scarlet Witch in Age of Ultron, where all of his friends were dead at the hands of aliens.
Ultimately, Thanos was the personification of the extraterrestrial menace Iron Man had dreaded since the closing moments of The Avengers. At the beginning of Infinity War, it was a telling moment when Bruce Banner, Doctor Strange, and Wong explained the impending threat of Thanos to him and Stark exclaimed "This is it!" Stark even told Thanos so to his face when they fought on Titan: "My only curse is you." And as Stark told Strange when they commandeered Ebony Maw's ship to get to Titan, Thanos had been living in Tony's head "for six years." (This is something that continues to perpetuate the MCU's broken timeline.)
Tony Stark had long feared "the endgame" Thanos represented and he was forced to watch as Peter Parker and his allies died thanks to Thanos' finger snap. The Mad Titan succeeded in doing the unthinkable, and Iron Man not only couldn't stop it, but he survived while untold billions perished - which is a new form of torture to Tony. Perhaps Avengers 4 will see Stark enact an endgame of his own that will finally defeat Thanos. What Iron Man does next is the question Avengers: Endgame will answer. But whatever does happen, it will hopefully end the personal demons Tony Stark has been haunted by for nearly a decade, which he tried to explain to his fellow Avengers when he told them about "the endgame" in Avengers: Age of Ultron.