Personally, I always feel like Tony trying to kill Bucky just doesn't work. I mean, sure, I understand Tony's a hothead. I understand, obviously, having his parents murdered is something that really fucks with him. But Bucky was brainwashed, Tony knows he was brainwashed, and it just feels really weak to have that be the thing that makes Cap and Tony duke it out. Especially because I feel like the philosophical difference between the two was actually really interesting and made for a much better driver of the divide between them. The Bucky thing just feels way too contrived, like oh I guess these guys have got to fight about something, so here we go.
I do like the movie overall, though.