In the pilot, Sydney is being tortured. After cooly telling her torturer that she's the one in control, as she's got "nothing left to lose", he tells her that's not entirely true - she has teeth. A look of terror crosses her face as he pulls out a pair of pliers. As he is about to yank out her teeth, she screams for him to stop, and then tells him... "Start with the ones in the back... if you don't mind." This was only the first of many, many Bad Ass moments.
In the 1st season finale "Almost Thirty Years," Will Tippin, a journalist who has uncovered the existence of a secret organization that is pretending to be part of the CIA has been tortured for several days. His torturer has taunted him with sodium pentathol saying that 1 in 5 men are paralyzed by it. The second that his captors loosen his bonds to transfer him back to Sydney, he grabs the needle full of sodium pentathol and jabs it in the neck of his torturer yelling "One in five, you little bitch! ONE IN FIVE!" at him the whole time.
Jack Bristow's in the series finale:
Jack Bristow: You beat death, Arvin... but you couldn't beat me. (presses detonator).
Marshall gets plenty gadget-wise.
Hacking the world's most secure... game of PONG in "A Higher Echelon". And then grabbing Sydney, employing Chekhov's Parachute, and jumping out a building with the line "Hello, my name is Marshall J. Flinkman and I'm here to rescue you!"
Amy Acker's scene stealing turn as Kelly Peyton reaches its apogee in the episode 'Maternal Instinct' when she destroys a helicopter with an RPG.
After giving us a whole season of Awesome, Irina reaches her peak when she leaps off the roof of a 30-story building to escape the authorities in "The Telling".
And shoots out ten stories' worth of windows on the way down, slams into the side of the building, swings into a window, eludes an entire squadron of guards, and disappears into the night.
In "The Box" parts one and two, Sloane undergoes unspeakable torture at the hands of McKenas Cole, refuses to give up the pass code Cole wants, laughs in Cole's face, and tells Jack to cut off his finger prevent an explosion that will kill them all.
Sydney to an interrogator in the pilot asking who she works for: "Write this down - E.M.E.T.I.B. You got that?... Okay, now reverse it."