Derpy Hooves holding back a storm long enough for Rainbow Dash & Pinkie Pie to perform a Sonic Rainboom, all for the sake of her daughter Dinky.
Fluttershy leading the effort to hold back the same storm and save Ponyville, despite having almost no weather experience whatsoever. She works to the point where she drops out of the sky and the other pegasi have to catch her.
Nightmare starts two Break the Cutie fights. First one, Pinkie breaks through the barriers and helps Rainbow win. Second, when Nightmare goes for the He's Dead, Jim kill, Pinkie takes it on herself. Battle in the Center of the Mind is generally where you find who will stand up, and she wins three rounds. Then turns it around and breaks the villain by going in for round FOU; invading Nightmare's mind.