New features
Features
A new difficulty mode called Critical Mode.
Textures redone with a better definition.
A new Drive Form called "Limit Form" has abilities from Kingdom Hearts and Kingdom Hearts Final Mix, and also bears resemblance to Sora's outfit from the original game.
A new mini-game called Puzzle, which unlocks special items.
Many Heartless received palette swaps.
Storyline
New cutscenes based on the Kingdom Hearts II novels were added; some involve Roxas, including scenes of him conversing with Axel in Twilight Town while wearing the Organization's signature black coat. There are also additional scenes of Roxas and Riku, including shots of their second battle, where Riku takes on the form of Ansem, Seeker of Darkness, Naminé leaving with Axel, Riku and Sora talking before they battle 2nd Armored Xemnas, Xigbar and Zexion talking about Xemnas, and the Organization discussing their plans and commenting on incidents like Axel's death.
Zexion's weapon is revealed - a large book called a "Lexicon", which he can use to trap his enemies in an alternate reality.
Battles
Members of Organization XIII that were eliminated in Kingdom Hearts: Chain of Memories can be found and fought in the various worlds of Kingdom Hearts II Final Mix. They each use different fighting tactics from the ones they employed in Kingdom Hearts: Chain of Memories. They include Vexen, Larxene, Marluxia, Lexaeus, and Zexion.
An area of Radiant Garden, called the Cavern of Remembrance, can be accessed. It houses a series of battle simulations with each member of Organization XIII. This is a separate feature from the secret battles with the Kingdom Hearts: Chain of Memories Organization members in that the simulation allows the player to repeat any battle with an Organization member as often as they like. The simulation features highly powered-up Organization members, similar to the level bonuses offered to enemies in the Hades Paradox Cup.
A battle against the mysterious Lingering Will can be unlocked at Disney Castle.
Battles with the Mushroom XIII can be fought.
The battle between Sora and Roxas in the Station of Awakening is made playable.
Bonuses
A "Theater Mode" - menu where previously viewed cutscenes can be watched again with either English or Japanese voices by pressing L2 and R2.
A new secret ending video titled "Birth by sleep", a teaser for Kingdom Hearts Birth by Sleep.
Secret features can be accessed in Kingdom Hearts II Final Mix by clearing Kingdom Hearts Re:Chain of Memories, and vice versa.
Roxas's story is expanded in Kingdom Hearts II Final Mix, including his fight with Riku.
A Crown, Bronze, Silver or Gold, can appear on Sora's head for defeating the following in any order:
All Mushroom XIII Heartless
All Data Battles
Lingering Will
These can be unlocked once the player gets a Clear Game Data
Twilight Town Changes:
Conditions to end the battle in front of the station have changed (Either connect 100 hits, go below 30% health, or battle for ninety seconds)
Addition of Limit Form Mirror in the Mysterious Tower
Hollow Bastion Changes:
After the event with Sephiroth, a scene with Yuna and the others flying out of a hole in the castle wall is shown
Land of Dragons Changes:
The morale gauge depletes at quicker intervals requiring the player to finish the missions faster.
Value of surprise attack spirit gauge has been reduced
Carts and boxes dont reappear after leaving the screen and returning (so you cant get drive balls so easily)
Beast's Castle Changes:
Conditions to end the battle in the Parlor have changed (Either connect 100 hits, go below 30% health, or battle for ninety seconds)
Cogsworth gets tired more easily
Olympus Coliseum Changes:
The time limit for which the player must defeat Pete, while protecting Megara, has changed from 2 minutes to ninety seconds
Disney Castle changes:
Enemies do not drop prize boxes while protecting Minnie
Timeless River changes:
Changes have been made to the four time window battles
Agrabah changes:
Conditions to end the battle in the street have changed (Either connect 100 hits, go below 30%, or battle for ninety seconds)
The battle at the Sandswept Ruins has changed (enemies do not drop prize boxes and the time to activate the switches after examining the monument has increased from thirty to forty-five seconds)
Halloween Town changes:
New costumes and music in Christmas Town
100 Acre Wood changes:
Time for Episode 4 changed from three to five minutes
Episode 5 rules have been changed
Drive Forms are available in minigames
The World That Never Was changes:
Xigbar changes his gun movement when attempting to snipe you from above.
Addition of Critical Mode:
Compared To Standard and Proud, enemies inflict twice the damage, except for the Mushroom XIII who inflict 1.25× the damage
Several abilities are granted on the third day (Reaction Boost, Finishing Plus, Draw, 2x Lucky Lucky, MP Hastera and EXP Zero)
Roxas's initial AP is 50
AP increases by increments of 3 instead of 2
Compared to Standard and Proud, HP and MP quantities from Bonus Levels are halved (You only get sixty instead of 120 HP)
Compared to Standard and Proud, EXP gained is three-quarters of the normal amount
Save file displays "Critical Mode"
Unlocking the "Birth by sleep" video just requires you to win the Gold Crown
In the PS2 Browser screen, there is a symbol attached to the save data file on the memory card
Filling the Drive Gauge is easier and the maximum "level" for the Drive Gauge has increased to nine
New weapons and accessories:
Winner's Proof
Executive's Ring
Highest Ribbon
Spell's Relic+
Akashic Record+
Frozen Pride and Frozen Pride+
Centurion and Centurion+
Shade Archive and Shade Archive+
Full Bloom and Full Bloom+
Shock Charm and Shock Charm+
Two Become One
Pleasure Mushroom, Pleasure Mushroom+, Precious Mushroom , Precious Mushroom+, Premium Mushroom
Happy Mushroom, Happy Mushroom+, Palatial Mushroom, Palatial Mushroom+, Limited Mushroom
