In no particular order
1. Rufus staring down diamond weapons as it blew him to hell/
2. Cloud finally regaining his memory, and the scene where even after being stabbed, he lifted Sephiroth up and flung him into the Mako reactor.
3. Bahamut, Alexander, and Alexandria being nuked by the invincible.
4. Odin wiping out Cleyra.
5. The Alexandrian attack on Lindblum, Atomos sucking up the tower.
6. Delita being stabbed by Ovelia.