I was just waiting to see so many of Jack's old allies come back to save him and fight back at the very last minute; I was not disappointed, quite the contrary. The woolies, The (no longer) blind archers, the rave teens, the dogs from the premiere movie, the Scotsman and his army of daughters, etc....almost everyone! They didn't do much against Aku until later on (probably why they opted not to have any lesser antagonists like Scaramouche or Demongo participate in the final battle; Aku hardly needs an army to battle another army when he can completely take it down all on his own) Thankfully however, this one was still able to really hold out. Thank you Scotsman!
The fact that Aku broadcasted the old intro in-universe was just wonderful. It's kind of like a tie-in explanation of why Aku narrated it of sorts; Aku's probably broadcasted it plenty of times before to explain his current position in his new world.
It was heartwarming seeing Jack just smile at the sight of all his old friends and allies, and his interaction with the Scotsman again, even if he's a ghost. I do kinda wish they would've gotten to interact a bit more, but ah well. It was good for what it was.
Oh, and Aku's reaction when he realized Ashi used her newfound Aku powers to take them back to the past? So satisfying. All it was was a quiet "Oh no...". He knew he was done for at that point. He just knew.
Ultimately, the ending was bittersweet since Ashi could no longer exist with Aku's timeline was erased (I don't think it had to do with Aku himself being destroyed; her reaction upon his initial destruction seemed more like she felt his death than anything else) and she ceased to exist moments before she and Jack were wed. It was tragic, and while she did become a memory like he feared....at least it's going to be a fond one, now that peace has been brought back to his world, Aku being no more. He's got his family back to comfort him, too, if no one else. Not to mention all of the other rulers he trained with over the years showed up in celebration, too. That was a really great throwback, and I'm glad they didn't miss the perfect opportunity to show them again.
It's been a great ride everyone. I know a couple other people here have said it already, but......hey, this show was a part of my childhood, so I feel I should say it as well: Thank you Genndy for giving us a conclusion to the wonderful story you started so many years ago. It was well worth the wait. It really and truly was.