Difficulty Level

The Difficulty Level of a game in the Kingdom Hearts series determines enemy strength and limitations the player will be presented with during gameplay. Players can choose a difficulty level to clear the game on when they first start a new game, but they cannot change difficulty levels once they have started. The hardest difficulty is Critical Mode, followed by Proud Mode, then Standard Mode, then Beginner Mode. Critical Mode is available in Kingdom Hearts Birth by Sleep, Kingdom Hearts II Final Mix+ and Kingdom Hearts Re:coded. The first time Proud Mode became available was in Kingdom Hearts II and has been in all games since. The only Kingdom Hearts game with no difficulty level was Kingdom Hearts Chain of Memories which was set at Normal most likely.

Kingdom Hearts

 * Beginner Mode
 * Normal Mode
 * Expert Mode
 * Proud Mode

Kingdom Hearts II

 * Beginner Mode
 * Standard Mode
 * Proud Mode
 * Critical Mode

Kingdom Hearts Re:Chain of Memories

 * Beginner Mode
 * Standard Mode
 * Proud Mode

Kingdom Hearts 358/2 Days

 * Beginner Mode
 * Standard Mode
 * Proud Mode

Kingdom Hearts Birth by Sleep

 * Beginner Mode
 * Standard Mode
 * Proud Mode
 * Critical Mode (Only in NA/EU versions and Final Mix)

Kingdom Hearts coded and Re:coded

 * Beginner Mode
 * Standard Mode
 * Proud Mode
 * Critical Mode

Kingdom Hearts Final Mix

 * Player starts off with a Ribbon, an EXP Chain, 8 Power Ups, 8 Guard Ups and 4 AP Ups.
 * The Drill Gummi's Attack Power is 9,999, instead of 35.
 * Another Side, Another Story [deep dive] is not accessible.

Kingdom Hearts 358/2 Days

 * Player sustains x0.7 damage.
 * HP prize recovery is doubled.

Kingdom Hearts Birth By Sleep

 * Player deals 50% more damage.
 * All damage dealt to player is halved.
 * Blank Points is not accessible.

Kingdom Hearts Final Mix

 * Gummi Ship takes double the damage.
 * Damage inflicted by the player is cut by a third.
 * Must complete the Hades Cup; find all 99 Puppies; seal every Keyhole; and complete Jiminy's Journal to unlock Another Side, Another Story [deep dive].

Kingdom Hearts II

 * Player deals normal damages.
 * Damages dealt to player is normal.
 * Must complete Jiminy's Journal to unlock The Gathering.

Kingdom Hearts 358/2 Days

 * Player sustains normal damages.
 * HP prize recovery is normal.

Kingdom Hearts Birth By Sleep

 * Player deals normal damages.
 * Damages dealt to player is normal.
 * Must complete the Report Section and Final Episode to unlock Blank Points.

Kingdom Hearts Final Mix

 * The Gummi Ship's attack deals half the damages.
 * A "Battle Report" is shown at the end.
 * Must seal every Keyhole and complete Jiminy's Journal to unlock Another Side, Another Story [deep dive].

Kingdom Hearts 358/2 Days

 * Player sustains x1.75 damages.
 * HP prize recovery is x0.7

Kingdom Hearts Birth By Sleep

 * Compared to Standard and Beginner mode, the player deals half the damage.
 * Compared to Standard and Beginner mode, enemies inflict twice the damage.
 * Must complete the Final Episode to unlock Blank Points.

Kingdom Hearts II: Final Mix+

 * 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 60 HP 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 Playstation 2 Browser screen, there is a symbol attached to the save data file on the memory card.

Kingdom Hearts Birth by Sleep

 * Compared to Standard and Proud mode, the player deals half the damage.
 * Compared to Standard and Proud mode, enemies inflict twice the damage.
 * Compared to Standard and Proud mode, HP and MP quantities from Bonus Levels are halved.
 * Game begins with five command slots.
 * EXP Zero is available as an ability.
 * Unlocking the Blank Points video requires you to complete the Final Episode.

Mission Mode
Though not a difficulty level in itself, Kingdom Hearts 358/2 Days's Mission Mode boasts a difficulty level of its own, that surpasses even Proud Mode in the same game. Regardless of what difficulty you play on in Story Mode, Mission Mode's difficulty stays consistent. Due to its intended multiplayer purpose, designed for two or more players to cooperate, players deal far less damage than usual. With the bonus defense from automatic higher levels for enemies in Mission Mode, players only deal 0.5x damage, and take normal damage.

Trivia

 * Kingdom Hearts Birth by Sleep's NA/EU release was the first time Critical Mode was implemented outside Japan.
 * Kingdom Hearts Re:coded allows interchangeable difficulty levels within the Status Matrix.