"Doesn't matter what the press says. Doesn't matter what the politicians or the mobs say. Doesn't matter if the whole country decides that something wrong is something right. This nation was founded on one principle above all else: The requirement that we stand up for what we believe, no matter the odds or the consequences. When the mob and the press and the whole world tell you to move, your job is to plant yourself like a tree beside the river of truth, and tell the whole world — 'No, YOU move.'"
"I have sworn many oaths in my day, to every being from Hoggoth to Watoomb. But the first oath I swore was the Hippocratic. 'I will prescribe regimens for the good of my patients, according to my judgement and ability, and I will do so at any cost.'"
Iron Fist: "I am the Iron Fist. I stand before the unstoppable hordes... and I hold them back. That's what I do. What I've always done. I am the Iron Fist. I hold back the storm... when nothing else can."
Wolverine: Wolverine’s "I'm the best there is at what I do — but what I do best isn't very nice." The second part is frequently dropped.
Films
The Avengers have a short but emphatic one, emphasised in the trailers, in Avengers: Endgame about undoing the Snap: "Whatever it takes."
There’s also Nick Fury’s description of the team, appearing first in The Avengers (2012) and later, in a slightly modified and shortened form, in the trailer for Avengers: Infinity War:
There was an idea: to bring together a group of remarkable people. To see if they could become something more. To see if they could work together when we needed them, to fight the battles that we never could.
