- Celestia executing Luna.
- What happens to Gilda at the end.
- Fluttershy blinding the Red Dragon, which then commits suicide.
- What Rarity does to the lead Diamond Dog when he resists her brainwashing.
Rarity: A disobedient dog should be put out of his misery.
Nightmare Fuel / Friendship is Betrayal
You can guarantee that almost every arc will end with at least one.