Well, doesn't that admission cut right through Bruce? Tony feeling broken or inadequate is different from him being actually, physically, zapped-himself-with-gamma-rays broken (or this serum, or any other serum, etc.), but Bruce can't go around saying that. That's his opinion; Tony clearly has another one. The fact that he took out the reactor should say a lot, especially compared to his speech on the helicarrier to Bruce about how much it meant to him. He's clearly in a different headspace.

It takes Bruce all the way to the end of Tony's sentence for him to figure out who the him is, and then he clenches his jaw and looks away.

"You really want to be immortal?"