Let’s talk about the sheer, simply brilliance in the way Tony Stark pierced Bruce Banner’s shield.
Bruce is, or once was, a truly depressed and damaged man. He sees himself as a monster, perhaps a failure at life and science for becoming one, and had gone as low as attempting suicide and even failed at that. He had sunk into obscurity, seeking peace in solitude and had long accepted that humanity in general will fear him, loath him, tiptoe around him, and forever see him as a monster.
He was not prepared for Tony Stark, who in his own simple, arrogant, self-absorbed way, ignored literally everyone’s perception of Bruce and formed his own opinion of the man before even meeting him. He walked in and commented on the hulk in the room as casually as if he was complimenting Bruce’s shirt. One could almost see his mental process upon seeing Bruce - “my age - cool; seems nice - cool; almost as smart as me - double cool; big green months thing - bitchin’”.
Tony Stark had likely decided before even meeting Bruce Banner in person that they were going to be friends. No matter how anyone else tiptoed around Bruce, Tony treated him like he did anyone else, by being a friendly, charming, outgoing, and generally irritating prick. His casual manner around Bruce allowed Bruce to relax around him. Just by being himself, he told Bruce wordlessly that it’s OK, there’s much more to him than the monster inside, and someone sees that.
It wasn’t so much that Tony wanted to show Bruce he didn’t care about the monster - he truly, genuinely did not care. He’s Tony “genius billionaire playboy philanthropist” Stark. He couldn’t be bothered with some little medical problem his new BFF has on the side. It just wasn’t a big deal. Not when there’s so much science to be done and so many toys they could play with together.
And all Bruce ever needed was for his big problem not to be someone else’s big deal.