Awesome / Old Mare Luna

• When Tirek's goons were beating the crap out of Luna, Gail quickly got his shotgun and fended them off with a warning while saying, in the Canterlot Royal We "Thou shalt CEASE!". Keep in mind that he is just a young colt.
• In a flashback, when Grogar offers Discord that he can resurrect Fluttershy in exchange for Flurry Heart. Here is what Discord had to say to that:
  Discord: Two Words: No. Deal.
• Luna vs Chrysalis. Thanks to Chrysalis' throne disabling all types of magic except changeling magic, Luna had to rely on nothing more but her own physical strength. Even better is that the fight lasted for twenty minutes. While Chrysalis does win the fight, it turns out that Luna was merely distracting her long enough for Discord and the changelings they brought with them to destroy Chrysalis' throne. When Chrysalis found out about this, she angrily charged at Discord, which proved to be a mistake because that opened her up to Flurry Heart killing her.
• Grogar brutally killing King Sombra when Sombra no longer wishes to honor their deal. It goes to show that Grogar isn't called the "Father of Monsters" for nothing. It's also incredibly satisfying given Sombra's actions in the story.
• When Grogar was about to execute Luna, Discord and Settler, they were all immediately rescued by the Dazzlings and Pharynx disguised as guards. Given what Grogar is capable of, that takes some serious balls. There is also the fact that the Dazzlings have been turned into earth ponies and were scared of Grogar when they first encountered him (except for Sonata because she didn't know who he is).
• The fight between Discord and Cosmos, especially since it was a Curb-Stomp Battle in Discord's favour.
• Luna, who has turned back into Nightmare Moon, taking revenge on Tirek for him killing her family. First, she eviscerates all of Tirek's forces in gory fashion, then she puts up quite the fight against Tirek (who has grown to the size of a mountain at this point) and, when it seems Tirek has defeated her and eaten her, she bursts out of his chest and kills him for good.