Rarity: Just put yourself in Fluttershy's position, dear! Her friends are all down, and that red dragon is gloating over them. Fluttershy might be feeling righteous outrage at what this dragon is doing to her friends. Imagine you are Fluttershy in that situation. What would you do? What would you say?
Rover: See?! The true hypocrisy of po-nies — hugs and friendship following lots of violence! Rarity: You tried to enslave me. * Beat Panel* Rover: Uh... It was supposed to be ironic?
Followed by her extending a very generous offer to the Diamond Dogs — with the underlying threat that they could 'bargain' with Rainbow Dash instead of they don't care to cooperate.
After a much-needed pep talk from her friends, Rainbow Dash gains the favor of the dice with a well-timed natural 20.
Then there's her proceeding to keep perfectly in-character while turning down the Wonderbolts: "I already HAVE a party."
In the Smarmony Returns guest comic, the party averts TPK by dragon by exploiting each character's powers and clever rule abuse to enlarge a pet throwing rock to deal 24d6+12 damage. The kicker: the rock was named Thomas. Derpy puts it best.