Warning: this post will contain spoilers, so read my post at your own RISK!
Ok, here it goes...
I LOVED THE FINAL, except for a couple of things, but I'll get to that in a moment. My favorite story arks is with Finn and Fern settling their differences, and Simon and Betty seeing each other again for the final time.
Favorite Story Arc 1: Since Finn is my favorite character, we finally get to see Finn and Fern beat their fears and shared torment from Finn's vault. It really excited me that Finn got to see the Embassy from Beyond, AKA, the Grass Demon, that consumed the Finn sword, and turned in to Fern. I thought the way Fern died REALLY reminded me of the way Spider-Man died in Avengers: Infinity War! Peter: "Mr. Stark, I-I don't feel so good". Fern: "Hey Finn, I not doing so good." Total Avengers: Infinity War reference!
Favorite Story Arc 2: After the Gumwar, which flopped in a good way or a meh way, Normal Man appeared from Golb's dark dimension, and said that he screwed up really bad! It seems like Betty found another way to cure Simon, but that didn't seem to work really well. We get to see Ice King and Betty fall into Golb's mouth, along with Finn so he can rescue Ice King and Betty (btw Finn lost his robot arm, and I was surprised that because Finn didn't care about his robotic arm being missing, but I guess he's tough enough to live without), but they we're trapped in a red box inside Golb, which made me REALLY tense up, and got to see Ice King and Betty go back to their original essential forms, which cured Simon from the Crown's power, since the Crown's jewels power got sucked out by Golb. When the red room got smaller and smaller, it kinda made me feel very tense, because I was almost afraid that Simon, Betty and Finn wouldn't escape from Golb, but thankfully BMO's song, Time Adventure, saved them from near death. Man, this story ark really put me on the edge of my seat! I couldn't believe it!!! I'm glad Simon got cured, and he can continue to live his life. Btw, I thought Gunter turning in to Ice King was really funny! I guess Betty trying to wish with the crown wasn't working. I was surprised when Betty and Golb fused together, which was totally weird to me, and Normal Man was all like, "What has she done?", and a very unique pencil sketch animation style popped up from Golb that made him look like a demon forming in to a Betty/Golb hybrid. I have never see anything like that before in Adventure Time!
A few other things I liked about the Final: The Intro was pretty cool, because it showed us the distant future of OOO again, along with the first part of the episode, and last part. I did like Shermy and Beth the Pup Princess, and for some reason, I kinda see an Adventure Time spinoff show for those 2 characters. I really liked how they put BMO as the new King of OOO! I thought that was AWESOME! I liked the interaction with LSP and Lemongrab. I thought it was pretty funny, because they have so many relatable things that they have. When Golb's monsters didn't like the song BMO sang to Jake, and then everyone else sang BMO's song, it really reminded me of Yellow Submarine when the Blue Meanies retreated away from Sgt. Pepper's Lonely Hearts Club Band or The Beatle's performance. That's a great Yellow Submarine reference! I loved the way Fern turned in to a Finn Sword seed, and Finn got to plant it where the Tree House once stands, and after Finn planted the seed, we got to see...... THE FINN SWORD AGAIN!!! YES! One of my favorite swords got to come back for the Final episode! I'm very happy to see it again, especially the very last scene where Shermy got to hold the sword up in the air! That scene is just AMAZING! I loved the way they showed all the characters at the end to show what happened to them after the Gum War and the Golb situation. I was really surprised that they showed a few characters that are still alive and well, especially TIFFANY! I don't know HOW he survived!
The things I didn't like about the Final: I wasn't really excited about the Gum War. At first I was tense about it, but it flopped and turned in to a nightmare sequence of PB and Gumbald fighting, which was interesting but kinda ok. Jake's dream sequence kinda felt like a filler time slot to me. The interaction with PB and Marcy I HATED! It reminded me of what The Legend of Korra did in the very last episode, but WORSE!
I can't believe we made it to the day that Adventure Time officially ended. I almost want to tear up, but I'm staying strong, because things don't last forever. Adventure Time got me in to being a very self-aware and mature person, with all the life lessons and fun it had in the show. I'm really going to miss Adventure Time, because I remember going in front of my TV set almost every time when a new Adventure Time episode get's recorded on to my DVR or seeing it live! I'm going to miss you Adventure Time, but I will always have you in my memories, and my Blu-Ray/DVD collection for years to come.