The moment you see Thanos’s significantly injured body in the first act of Avengers: Endgame, you recognize the devastating force of the Infinity Stones. If Thanos can barely survive using them, who will be the Avenger powerful enough to undo the snap? Because, if there’s one thing you know going into Endgame, is that a member of the team will bring everyone back. Then, when Hulk steps up and is quite hurt after snapping everyone back into existence. But it turns out that the effects of the Infinity Stones, as shown on Thanos and Hulk, are meant to prepare the audience for one of the most heartbreaking scenes of Endgame, the moment when Tony dies. There’s just no other way for the Avengers to win than for Iron Man to sacrifice his life to wipe Thanos and his army out of existence. As it turns out, however, Tony’s death was almost very different and far more violent.
Five members of the visual effects team who worked on Tony Stark’s death scene detailed to Insider the various proposals they submitted to Marvel for the scene in question. One of them involved the Stones popping one of Tony’s eyes out, per Weta digital VFX supervisor Matt Aitken:
We gave the filmmakers a full range [of looks] to choose from, and one of those was where the energy from the Stones had acted right up into his face and popped one of his eyeballs out, and it was hanging out on his cheek.
Another one had Tony looking more like Two-Face from The Dark Knight, as Marvel VFX producer Jen Underdahl said:
We did do a Two-Face version where you got inside, and you saw the sinews, and you saw them in the teeth and that
All that would have been too brutal and would have detracted from the highly-emotional scene. That’s something Marvel didn’t want to do. The purpose of showing Thanos and Hulk being hurt by the Stones was to prepare the audience for Tony’s death, and convey the message without resorting to showing a violent death for Iron Man — from the same Underdahl:
We had seeded in the film this notion of Thanos having damage. There are consequences to him snapping and pursuing this ideology. You see the damage in his face and what that did to him, and he’s built for this. Then [you] see the consequences to Smart Hulk, who was made of gamma radiation and the damage that it did there.
You knew somewhere in the math that Tony himself, even though he’s got this suit and it’s going to fight for him, ultimately what’s going to result would be something he couldn’t recover from.
The special effects team explained that, with any development item, they wanted to offer the filmmakers various choices for Tony’s death scene, from a light touch all the way to more horrific options, so they could land on exactly what they needed. And you can easily argue that Tony’s death scene is easily one of the highlights of Endgame. While it’s not as gruesome as it might have been, it’s still horrific for fans who realize this is the last time they’ll see Stark manning the Iron Man suit.