WARNING: This article contains SPOILERS for Spider-Man: No Way Home
Spider-Man: No Way Home makes Tony Stark's sacrifice even more tragic. Said sacrifice in Avengers: Endgame is already one of the saddest moments in the entire MCU. However, Spider-Man's latest solo outing (and his entire post-Endgame arc in general) make it even more heartbreaking than before.
Peter Parker and Tony Stark share a bond akin to a father-son relationship in the MCU. It's at the core of their emotional arcs, with Peter aspiring to be like Tony while the latter hopes he can be better. Furthermore, he also feels responsible for Peter's life, and if anything should happen to him, that's on him. Since he's the one who recruited him in Civil War, he does have a point, and it's when Peter Parker is lost to the Blip that Tony completely shuts down. It's also what inspires him to try and reverse it when Scott Lang arrives with a solution.
Tony Stark giving his life to undo the Blip in Avengers: Endgame is sad enough on its own. Spider-Man: No Way Home makes it more tragic by rendering it, to a certain degree and for the time being, completely pointless. Peter faces incredible hardship upon his return from being snapped, and by the end of No Way Home, everything Tony Stark has done to aid him in his quest is effectively erased. In essence, Tony's indoctrination of Peter is rendered inconsequential, as he has abandoned Iron Man's Avengers path and gone back to being a street-level crime fighter. The fact that, for now at least, Stark may have sacrificed himself for nothing, as far as Spider-Man goes, is yet another emotional blow.
While Spider-Man: No Way Home features Peter at his lowest point, his entire life post-Endgame isn't exactly the most welcome return. Not only does Peter struggle to come to terms with Tony Stark's death in Spider-Man: Far From Home, but he's also bombarded by people demanding answers on whether he's gonna be the next Iron Man or not. When it becomes too much, he turns to Mysterio in the hopes he'll take his place as a hero. In response, Mysterio betrays Peter's trust by using E.D.I.T.H. for nefarious purposes, endangering his friends, framing him for his crimes, and exposing his identity as Spider-Man.
These events lead into Spider-Man: No Way Home, where Peter tries to get Dr. Strange to erase everyone's memory of his being Spider-Man, and after accidentally causing Strange to make a catastrophic error, ends up releasing several villains from the multiverse. From there, his attempts to try and rehabilitate all the villains are nearly ruined thanks to Green Goblin, which ultimately results in Aunt May's death. Finally, when the multiverse starts to crack beyond repair, Peter offers to let Strange erase everyone's memory of him, which means he will basically cease to exist in the eyes of those who knew and love him. This clean slate also means he's no longer a part of the Avengers, and all the tools and gadgets he had thanks to Tony are no longer at his disposal. Effectively, by the end of No Way Home, Peter has cut himself off from Tony's legacy.
Spider-Man: No Way Home makes Tony Stark's sacrifice more tragic because everything he did to build up Peter as a hero is rendered moot, at least for now. He may save the entire world, but bringing Peter back is one of his major goals when reversing the Blip. As Happy put it in Far From Home, Tony wouldn't have left if he didn't know Peter would be there to pick up the pieces. Sadly, it's now going to be a lot harder for Peter to become the hero Tony knew he could be, but there's hope that that time will come once Tom Holland's new Spider-Man trilogy is released.
