Spike defeating Razorfang with the same rock that started the feud.
Spike managing to fly perfectly for the first time in order to save Fluttershy.
Fluttershy standing up to Razorfang to protect Spike, doubles as Heartwarming as well.
Fluttershy: You...big... jerk! You are wrong! We love him! He's - our - friend! We would never, never, NEVER turn on him! How dare you stand there, you big bully, and suggest that Twilight would ever hurt her own brother! How dare you tell him his own family would turn on him!
Twilight Sparkle: I know, right?
Fluttershy: You might be powerful, and lonely, and angry, but you have no right to say those things! How dare you spout off about something you know absolutely nothing about! Ponyville is Spike's, and Spike is Ponyville's, and there's nothing you or anypony else can do to change that! Now go back home to your Forest, and think about what you've done!
The Magician of Coal Crater pinning Razorfang to the spot with magic after he insults him. And the simple fact that a magic-resistant dragon is a magician in the first place.
Twilight hypnotizing Blarney Stone into confessing his crimes.