EXP Zero

EXP Zero (EXPゼロ), also known as "Zero EXP" and "No Experience," is an ability introduced in Kingdom Hearts II Final Mix. It prevents the party from gaining EXP as long as it is equipped.

This ability allows the player to complete the game without gaining EXP and thus remain at level 1, resulting in a more challenging play-through.

Mechanics
In Kingdom Hearts Final Mix, EXP Zero is a combat ability exclusive to Proud Mode that costs 0 to equip. It also prevents Sora from being knocked out in one hit at full HP.

In Kingdom Hearts II Final Mix, No Experience is a that costs 1 AP to equip. It negates normal EXP, but not the various types of Form EXP.

In Kingdom Hearts Birth by Sleep, Zero EXP is a exclusive to Critical Mode that can be equipped once.

In Kingdom Hearts 3D: Dream Drop Distance, EXP Zero is a exclusive to Proud Mode and Critical Mode that can be equipped once. It negates the experience gain for Sora and Riku, but not the Spirits.

In Kingdom Hearts III, Zero EXP is a that costs 0 AP to equip.

Kingdom Hearts Final Mix

 * Sora has EXP Zero as a default ability in Final Mix: Proud Mode difficulty.

Kingdom Hearts II Final Mix

 * Roxas learns No Experience at the beginning of the Third Day in Critical Mode.
 * The Winner's Proof has No Experience as its Equipment Ability.

Kingdom Hearts Birth by Sleep

 * Zero EXP is attached to Terra's Sliding Dash, Ventus's Aero, and Aqua's Blizzard at the beginning of their stories in Critical Mode.

Kingdom Hearts 3D: Dream Drop Distance

 * Sora and Riku have EXP Zero initially in Proud Mode and Critical Mode.

Kingdom Hearts III

 * Sora has EXP Zero as a default ability.

Kingdom Hearts II
While in Antiform, Sora does not gain EXP from defeated enemies similar to No Experience.

Kingdom Hearts 358/2 Days and Kingdom Hearts Re:coded
Although EXP gain cannot be disabled in either game, level ups only occur when Level Up panels are installed. Not installing them has the similar result of keeping the player at Level 1.

Kingdom Hearts 0.2 Birth by Sleep -A fragmentary passage-
EXP Gain is a setting that only appears in the options menu after beating the game. Disabling it creates an effect similar to EXP Zero.