Tony Stark's death in Iron Man the swan song he deserved.
While Tony's arc in the franchise ended in his tragic demise, it made sense in of his personal narrative. There's poetry in seeing him sacrificing himself to defeat Thanos and his minions for the greater good after starting as a self-absorbed, war-profiteering industrialist. Wielding the Infinity Stones and declaring "I am Iron Man" may be the most obvious reference to his origin movie, but Endgame featured a lot more callbacks to the Jon Favreau movie which helped ensure Tony's story was fully completed.
Marvel is known for playing the long narrative game, including seemingly unimportant details in their movies that become significant in later entries. Tony's death wasn't something that was planned from the get-go, since Iron Man was a huge risk and no one could've predicted how the MCU would thrive after its release. Still, there's one line from the blockbuster that was accidentally proven right more than a decade later in Endgame. During the opening sequence of Iron Man, Tony mingled with military officers, one of whom asked for a photo. As the young soldier made a peace sign, the snarky billionaire joked he didn't want gang signs. He eventually relented and said "Peace. I Love Peace. I'd be out of a job with peace." A decade later, he didn't only lose his job, but his life for the sake of re-establishing peace and order in the universe following Thanos' decimation.
Giving a deeper meaning to what initially seemed like a throwaway line from Iron Man proves just how strong character themes are in the MCU. While this wasn't something planned by the filmmakers it's still impressive how much of where the heroes, particularly Iron Man and Captain America, final fates harkened back to their first outings. It's primarily the reason why Endgame was cathartic to watch, even when Iron Man sacrificed himself. All narrative choices made sense — at least in of where the characters were at that point in their respective journeys. Somewhat tragically, Tony even told Captain America in their reconciliation scene that he "just wanted peace" suggesting there may have been a level of subconscious self-awareness about his fate.
The MCU will definitely feel and look different without Tony Stark in it, but while he's gone and his personal story finished his presence continues to loom large. Future projects like Avengers: Endgame, it's difficult to argue that it doesn't make sense considering how he started in Iron Man.
