Loyal Defender

Finally reached the final boss of KH 2. BUT FIRST.
A crap ton of side-stuff.
Find all chests
Collect all stickers and put them together
Play every minigame (saving the Underdrome for last)
Synthesize every item
Unlock the Ultima Weapon
Level up to 99 
Complete every Underdrome Challenge (saving any solo runs and time attacks for postgame, after reaching level 99)

AFTER BEATING THE GAME -
Take on the Underdrome ‘bonus’ challenges.
Battle in all 5 Absent Silhouettes
Complete any new synthesis recipes dropped by the Absent Silhouettes
Fight all 13 data-versions of the Organization Members
Find and Duel with all 13 Mushroom XIII
Fight the optional bosses (Sephiroth in Radiant Garden, Lingering Will in Disney Castle)
completing every Gummi Ship mission 100%,
and filling in EVERY journal entry.