Dark Qiviut

+ Really, really sweet of Twilight to name Spike her Friendship Ambassador, and the reasons why make this exchange all the more heartwarming.

+ Twilight's completely justified to doubt her worth as princess, fighter, and defender.

+ The RM6 were really good, and despite their separation, all seven were competent.

+ The Young Six shine once more.

+ The stakes are at their highest. Tone got dark and light at appropriate times.

+ The Terrible Trio:

1. show their full power potential and use it to bully Equestria, even to the point of threatening to maim Spike and almost murdering all seven. Their stone sentence is absolutely justified.
2. are justified not to use any of the magic, even though they store it in Grogar's Bell. If Cozy Glow can't control Discord's magic, what would happen should they become one with Celestia's and Luna's? (Twilight had a boatload of trouble when she borrowed the AliTrio's to keep away from Tirek.) Becoming part of that magic's more different than eating it.
3. Are a very credible threat beyond just the physical presence. They fought for power and worked together to resolve their differences despite the bickering. It makes the most sense for them to be the final baddies of the show and really commit crimes far beyond anything anyone committed up to this point.

+ The Mane 7 have been instrumental in bringing peace and harmony throughout Equestria and beyond. It only makes sense for everyone else to return the favor. This battle brings their teachings full circle.

+ Starlight is the Element of Badass!

+/- Celestia and Luna were initially defeated easily, but in their second chance to hold them back, they put up another fight and held them off for quite a while.

- The Terrible Trio were also incompetent at the worst time. You already stole the magic of Celly, Luna, Discord, and the Pillars. Why didn't you steal Starlight's when you had the chance?

- Discord being Grogar is a poorly-written, overcomplicated twist that created a long host of massive implications over the season, and despite the massive stakes, the consequences of his stupidity were downplayed. No, he didn't need to be turned to stone, but he needed some level of punishment to make him fully understand how bad his actions were and how he almost contributed to the leads' demises.

- The disharmony between the Earth Ponies, Unicorns, and Pegasi gathered absolutely no momentum whatsoever. After Setback, this subplot was tucked away for the rest of the season until here. If we had seen some of this discord at points, it would make sense. But here, it went from no momentum at all to happening immediately. It's jolting and contrived. As easily as the Terrible Trio were in sowing disharmony and havoc, the Young Six and other students easily made them reunite, making the B-plot and Windigoes pointless. Remove it and instead just have the Young Six rally the troops as normal, you get the same story.

- Because of this, the Young Six's impact feels slight

- Twilight's realization that the Elements were just symbols was sudden and had no weight. One minute, she didn't know if they were tangible and only belonged to those special, and she realized they weren't the next.

- The leaks showed that Ending of the End had an extremely complicated story that bit off way more than it could chew. Even after cleaning some of the crap up, the same problems didn't go away. There was a main plot and several subplots with the big twist that was planned from the start, but because it was only done in two parts instead of three, DHX really rushed through all the points without putting so much proper weight on any of them aside from one: the RM6 consoling Twilight when she was at her most frightened and vulnerable (the moral this scene taught was great). The Windigo B-plot could've been really good had the seeds been planted throughout, not get dumped on at the last minute, and greatly impacted the story.

- Even after Twilight and company defeated the Terrible Trio, they almost let them escape! If Pinkie didn't tap into Discord's chaotic powers and let a house-sized cupcake land squarely over them, they would've escapes and possibly tow Grogar's Bell with them.

Overall, Ending of the End's okay. I like it, but like A Canterlot Wedding, it could've done much better. Other finales and premieres are better.