How we cite our quotes: All quotations are from The Avengers.
Quote #1
STEVE ROGERS: Big man in a suit of armor. Take that off, what are you?
TONY STARK: Genius, billionaire, playboy, philanthropist.
STEVE ROGERS: I know guys with none of that worth ten of you. I've seen the footage. The only thing you really fight for is yourself. You're not the guy to make the sacrifice play, to lay down on a wire and let the other guy crawl over you.
TONY STARK: I think I would just cut the wire.
STEVE ROGERS: Always a way out... You know, you may not be a threat, but you better stop pretending to be a hero.
TONY STARK: A hero? Like you? You're a lab rat, Rogers. Everything special about you came out of a bottle!
STEVE ROGERS: Put on the suit. Let's go a few rounds.
Rogers and Stark basically jockey for position from the very beginning, but what are they jockeying for? Well, they're the two most natural leaders of the group, and while they may not be entirely aware of it, they're determining who gets to sit in the big seat.
Quote #2
THOR: You people are so petty…and tiny.
Thor's got a big streak of jock jerkwad in him, and while he mostly put that behind him in the first Thor movie, it still comes poking out from time to time. Ratchet it back there, Blondie; we got bigger fish to fry.
Quote #3
THOR: Our father...
LOKI: Your father! He did tell you my true parentage, did he not?
THOR: We were raised together, we played together, we fought together. Do you remember none of that?
LOKI: I remember a shadow, living in the shade of your greatness. I remember you tossing me into an abyss, I who was and should be king!
There's no rivalry like sibling rivalry. The competition is dialed up to 11 with these two: it's all "Daddy loved you best" and "You're not my real brother," coupled with thousands of years of getting under each other's skin.