Oh my, Xemnas is a pussy compared to the other fights, he goes down easy and fast. I died the first times because the glitch thing (I thought I was doing something wrong until I read info posted here), but this time I did Sessions every time and that's it, the rest of the fight is just Reflega+Quick run all over the place.
Now that I've done all the fights I'm rating them in fun factor, just because:
1- Marluxia. Clever mechanics, lots of variety, clear pattern. It's a blast.
2- Zexion. Way more fun than expected, getting sucked into the world book, understanding what you have to do to get out and punish him is great!
3- Xigbar. Because you have to guard a lot, and that is insanely fun in this fight for some reason. Seriously, he dies by eating his own bullets, that's amazing.
4 - Larxene. She is crazy, she is laughing all the time and she attacks nonstop. Love her and want to see her restored to her normal self to fight her again.
5- Saix. Another nonstop attacker, that's cool, but Larxene is better.
6- Roxas. Yet another nonstop madman, he would be higher if it wasn't for the lasers, which I hated. Screw lasers. And his RC actually makes the fight harder, no thanks.
7- Xaldin, OK, he is a little fun once you get the grip of things, but then again, once you arrive at that point he stops being obnoxious and becomes boring. If you really think about it, he only has one pattern than can really kill you (last phase).
8- Axel. If it wasn't for the floor on fire he would be too easy because he doesn't have that many attacks, but the floor mechanic is obnoxious, and the RC is exploitable. Meh.
9- Xemnas. Two phases. Each one of them easy as pie. BORING.
10- Lexaeus. Now, I still don't know what the fuck this guy does. I've seen guides when you have to block things? Whatever, just spam attack all the time and he goes down. Really, I don't know his patterns or attacks even after beating him.
Now, the absolute worst:
11- Vexen. Break shield, Final Form, spam Firaga, ????, Dead. He has some desperation move which creates spikes all over the place? Limit form and destroy him and Anti-Sora, his defense is pathetic. He could have been cooler, but he isn't.
12- Demyx. Even worse, just get into Wisdom, spam Firaga, when he creates pillars of water block and continue to spam Firaga. Boring.
And the worst one goes to...
13- Luxord! Fuck minigames, fuck having to pause to match circles and exes, what the fuck, screw you! I didn't have the patience to get through that, so I just spammed finishing moves. Now that it works, people, you don't have to do the command minigame, just the guessing where he is part. Then he enters the DM, pause (sigh) and kill him. Go to hell and don't come back, Luxord.
Now on to Lingering Will. I tried once before and he kicked my ass after draining two bars. He'll go down eventually.