Tony has always defended himself through evasive
manoeuvres, and never used shields.
Yet in Infinity War, he is using shields left and right. (The only time he shielded himself was in Iron Man 1, when he opened flaps in his gauntlet, and that was because he down low on power and couldn’t fly away.)
Tony realised that the team has lost a “shield”, so he took it upon himself to become one. He built a shield that could withstand the power of an Infinity Stone. Because he always knew the fight was coming, a bigger threat is on the horizon and he needed to be ready.
Meanwhile, Tony designed new shield for Cap (despite all the Civil War mess), new “magic” belt for Thor (despite not knowing whether Thor will return), ensured Hulkbuster was accessible to Bruce (despite Bruce being MIA) and built space-travel-safe spider-themed nano-suits for Peter (despite Peter not being an avenger yet).
Can you just imagine how much pain he is in right now? My brother got a small incision on his stomach and he didn’t move for days and he had drugs.
Tony just got shrapnel launched into his chest, a HUGE part of his chest crudely sawed out and a metal thing shoved in its place and he’s moving and walking around with it. All with no painkillers.
You know what I think about a lot? Tony Stark reeling in the
wake of Civil War, going on 72-hour work benders, trying to clean up everyone’s
mess and whip the Sokovia Accords into shape and rebuild the decimated team and
figure out how he can build Rhodey a new spine and forget about a metal hand
squeezing the life out of his mother, and when Happy reports back to him about Peter
he hates himself a little for holding the kid at arm’s length, but everyone who’s
in his orbit eventually ends up getting hurt and it’s better for everyone if he
keeps his distance, but that doesn’t mean he’s not keeping tabs on the kid and
sometimes at 4.30 in the morning when stress and anxiety and too much coffee
won’t let him sleep he sits in his office and listens to Peter’s inane voicemail messages and can’t stop the helpless smile from tugging on his lips as he learns about a
kind old lady buying the kid a churro and for a moment he feels a little less
alone and broken.