Chapter 1
Chapter 2
Speedrun tips
1 HP tips
The first portion of this level is rather easy at 1 HP. Like any other 1 HP run, save often, and when you have to fight swarms of Heartless, focus on long-range attacks—only use a Keyblade or close-range attack if there are few enemies, and your other commands are depleted.
Sweet jeebus the Keyhole is terrifying at 1 HP. Don't attempt it unless you can Glide and Air Dash. Your biggest danger here is getting hit by the falling blocks, so you should stay on the lower platforms as much as possible. You can tell when a block is coming by the screen shaking, but I'd honestly recommend watching a video playthrough so you know exactly when they're coming. (Ed: insert video link and list of falling blocks here) When you see groups of Heartless, use one of the special commands to take them all out at once.
Etc.
I'm going to do this. I'm seriously going to do this. Going to make myself do it.
Avatar Sector
The hardest part of the Avatar Sector is building it. You can use the communications exploit (Ed: remember to add info on the exploit to that article) to populate exactly fifty floors with default characters, but for the other forty, you'll need either a lot of friends or a lot of time. If you don't have that many friends, you're going to just leave your DS on, on tag mode. This will easily take up ninety hours of gameplay.
Now, you'll have to farm Tag Mode to get all 99 Puppies, but NEVER DELETE RANDOMIZED AVATARS. It takes forever to get even one replacement back. Once you've gotten all of the fifty default avatars (listed here), simply delete their floors and use the communications exploit again, but ONLY FOR THOSE FIFTY. It may take many, many rounds of tag mode and deletions, but eventually you'll have all 99 of the little bastards.
For the Avatar Sector itself, I recommend equipping the Ultima Weapon>>>>, with Clock abilities set to Heavy Blade, Undo, Attack Haste, and All Critical. As for your deck, I usually use Curaga, Zantetsuken, Gravity Drop, Judgment Triad, and Eruption, but you can replace Zantetsuken and Eruption if you want. For floors that require you to use Magic commands, I use Flame Fall, Triple Pursuit/Icicle Mine, Exo Spark, Cyclone, and Curaga.
If the floor requires you to ignite Heartless, equip the Wishing Star with Fire Counter; for freezing, equip the Oblivion; for jolting, equip the Olympia; for air-tossing, equip the Three Wishes. You will not be able to hinder Heartless like Defenders or Red Nocturnes, and you can't hinder Large Bodies when they jump on you or Fat Bandits when they shoot fire at you. Otherwise, just use your commands on Blox or un-hinder-able Heartless like these to build up your Clock Gauge, and once you have the correct Counter ability activated, go find something like a Soldier and just keep using Guard over and over.
The rest of the Avatar Sector is pretty straightforward. Its important to remember, though, that only the decim floors multiply your SP - fulfilling challenges on any other floor simply gives you an Avatar Part, so don't worry about the "play at night" or "play on the weekend" challenges if you're doing a 100 floor run. Furthermore, if you're going for huge amounts of SP, you don't have to kill every Heartless and break every blox—especially on the later floors, even an incidental hit from a Heartless will take huge amounts of SP away that you simply can't recover except by scoring a multiplier on a decim floor. Getting all of these multipliers is necessary to get the higher-tier rewards like D-Blizzaga and the stat chips, which are honestly the only thing you'd do this for anyway. Make sure to wager 50% every time. However, the top floors of the Avatar Sector are a wonderful place to farm EXP, so if you're going for Level 99, go ahead and kill everything you see. Encourage your inner psychopath.
(Ed: insert list of the decim challenges here, with tips on how to beat them)
For Eliminators...honestly, by the time you are ready to attack the Avatar Sector, you should be able to murder them easily. They are nothing compared to the regular Heartless you'll see on the final floors. Simply stay behind them and unleash your strongest commands. However, even on the final floors, most Heartless can be killed in one shot by a maxed Gravity Drop or Judgment Triad, though you should still make sure to dodge their attacks. Your biggest worries are bugged Wyverns or Invisibles, which can take off up to 10000 SP in a single bout. Keep your distance, and abuse Judgment Triad or Triple Pursuit. If you can trap one in a Keyblade combo, go for it, but try not to get hit.
The biggest feature of the Avatar Sector is obviously the bugged Data-Riku, but he's nowhere near as cruel as the bugged Data-Roxas. For example, his Dark Aura attack can be easily avoided by simply falling through the air, provided you start from high up enough, and you can always dodge normally if you land. Make sure to keep your health up, and simply attack him with Zantetsuken or Judgment Triad. Gravity Drop and Eruption are pretty useless against him, and the top-tier Magic Commands don't do enough damage. Like the bugged Data-Roxas, Data-Riku will go through every phase of being bugged, but unlike that cheating bastard, he never becomes immune to damage, and you should be able to take him down after several successful Judgment Triads.