NOTE: I have an updated, expanded version of this guide available at
Solution for Risk-taker In KINGDOM HEARTS IIIHere's the Sora setup I used to defeat all 13 Data Bosses in Proud Mode in less than two days:
Level 99, starting choices Balance & Guardian
Keyblades: Ultima Weapon, Classic Tone (both fully upgraded), empty third Keyblade slot (so it's easier to switch between the two)
Accessories: Crystal Regalia, Mickey Clasp, Flanniversary Badge [all for MP Haste]
Armor: Buster Band+, Cosmic Belt+ x2 [all for high Defense]
Items: Kupo Coin, Hi-Potion x8 [Auto-Reload] (Elixirs are better, but you can buy Hi-Potions at the Moogle shop)
Abilities: All of them except for two Attraction Extenders, Zero EXP, MP Safety, Counter Impact, & Counter Slash [and obviously Critical Counter, Critical Recharge, & Critical Converter] (farm AP Ups if you can't equip them all)
Cuisine: Lobster Mousse, Carrot Potage, Bouillabaisse, Stuffed Quail, Berries au Fromage (there are better foods, but these all can be bought at the Moogle shop)
Full Course Bonus: Cuisine Extender [There are better bonuses, but you can use the meals on more consecutive boss fights this way]
Shortcuts: Meow Wow Balloon, Hi-Potion, Curaga, Thundaga
Advice: Spam X with Ultima Weapon whenever you get an opening. Switch to Classic Tone whenever you're out of MP then back to Ultima Weapon when you're not. Use a Link instead of Curaga when your HP is low and MP is full. Make full use of Rage Form and Meow Wow Balloon until they expire or you're low on HP, in which case finish them with triangle. Seriously, a lot of my later boss fights ended with Meow Wow attacks.
Farming: If you're simply just not strong enough to beat all the bosses yet, farm materials for Attack and Defense Boosts to raise Sora's stats at Battlegates 10-12, making sure to have Favorite Deputy equipped on Sora, Lucky Ring equipped on a party member, and all instances of Lucky Strike in your party's abilities activated. You'll have to buy lots of Pulsing Gems for Pulsing Crystals for Strength Boosts, and that can get so expensive that you may need to farm munny as well.
List of XIII bosses in the order which I defeated them:
Larxene [She's the easiest, so I'd recommend beating her for the Start Analysis trophy]
Dark Riku
Marluxia
Young Xehanort
Vanitas
Xigbar [the trick is pausing until the X button prompt shows up in showdowns]
Terra-Xehanort [Meow Wow Balloon bounces were particularly helpful here]
Saix
Ansem
Xemnas
Luxord [the trick is pausing and viewing your surroundings in the card battles]
Xion [used a Master Medal w/ Stun Protection in place of Flanniversary Badge]
Master Xehanort [used a Snowman Rosette instead of Buster Band+]
Stats of various items:
Hi-Potion: Restores 160 HP to one teammate, 100 munny each
Elixir: Fully restores teammate's HP/MP/Focus & removes negative statuses
Megalixir: Fully restores team's HP/MP/Focus & removes negative statuses
Armor:
Snowman Rosette: +2 Def, +20% Blizzard & Dark Resist, Freeze Protection
Acrisius: +3 Def, +20% all Resist but Dark
Acrisius+: +4 Def, +20% all Resist but Dark
Royal Ribbon: +4 Def, +40% all Resist
Buster Band: +5 Def
Buster Band+: +5 Def, +10% all Resist but Dark
Cosmic Chain: +5 Def, +20% all Resist but Dark
Cosmic Belt: +6 Def
Cosmic Belt+: +6 Def, +10% all Resist
Master Belt: +7 Def, +20% Dark Resist
Power Weight: +3 Str
Magic Weight: +3 Mag
Accessories:
Skill Ring: +1 Str, +1 Mag, +30 AP
Skill Ring+: +2 Str, +1 Mag, +36 AP
Cosmic Ring: +3 Str, +80 AP
Master Medal: +1 Str & Mag, +6 AP, Stun Protection
Draw Ring: +1 Str, +2 Mag, +8 AP, Master Treasure Magnet
Lucky Ring: +1 Str & Mag, +8 AP, Lucky Strike
Star Charm: +3 Str & Mag, Damage Syphon
Cosmic Arts: +4 Str & Mag, Damage Syphon
Phantom Ring: +5 Str, +8 AP, Cure Converter
Orichalcum Ring: +6 Str, +10 AP, Cure Converter
Breakthrough: +7 Str, +15 AP, Cure Converter
Sorcerer's Ring: +5 Mag, +8 AP, MP Haste
Wisdom Ring: +5 Mag, +10 AP, Wizard's Ruse
Master's Necklace: +3 Str & Mag, +16 AP, MP Haste
Flanniversary Badge: +4 Str & Mag, MP Hastera, MP Thrift
Mickey Clasp: +3 Str, +5 Mag, MP Hastega, Endless Magic
Crystal Regalia: +5 Str & Mag, +16 AP, MP Hastega
Crystal Regalia+: +6 Str & Mag, +25 AP, MP Hastega
Starters:
Lobster Mousse: +1 DEF, +2 HP, +18 MP
Lobster Mousse+: +1 DEF, +4 HP, +20 MP
Soups:
Carrot Potage: +16 HP, +3 MP
Carrot Potage: +18 HP, +5 MP
Cold Tomato Soup: +1 MAG, +18 HP, +3 MP
Cold Tomato Soup+: +1 MAG, +20 HP, +5 MP
Crab Bisque: +1 MAG, +18 HP
Crab Bisque+: +1 MAG, +20 HP, +2 MP
Fish dishes:
Bouillabaisse: +2 DEF, +6 HP, +3 MP
Bouillabaisse+: +2 DEF, +8 HP, +5 MP
Sea Bass en Papillote: +2 DEF, +8 HP, +2 MP
Sea Bass en Papillote+: +2 DEF, +10 HP, +4 MP
Meat dishes:
Stuffed Quail: +2 STR, +1 DEF, +10 HP
Stuffed Quail+: +2 STR, +1 DEF, +12 HP
Desserts:
Berries au Fromage: +2 MAG, +8 MP
Berries au Fromage+: +2 MAG, +10 MP
Tarte aux Fruits: +1 STR, +2 MAG, +8 MP
Tarte aux Fruits+: +1 STR, +2 MAG, +10 MP
When you get Rage Form at full MP:
Fight 'til low HP
Use a Link
Finish the Link before Rage Form expires
Use Rage Form when low on HP or just before it expires, whichever's first
Addendums:
Simba is a better Link than Meow Wow.
Use Stun Protection against Xion, Dark Inferno, Saix, & Xemnas.
Master Medal (for Rank B in Flash Tracer A) and Nano Gear have it.
Use Freeze Protection against Master Xehanort, Young Xehanort, & Vanitas.
Snowman Rosette and Crystal Snow have it.
Terra-Xehanort: Block all of his projectiles, then airstep to combo him.
Elixirs can be bought at the Moogle Shop for 4000 munny each.
Shortcuts: King's Flare, Hi-Potion, Curaga, Thundaga
Replace Buster Band+ with Master Belt when you get it. And Flanniversary Badge with Crystal Regalia+.