Crisis Core: Final Fantasy VII/Buster Sword Proficiency

In Crisis Core Reunion, when you obtain the Buster Sword in Chapter 6, you also have access to a Battle Stance and a Buster Sword Proficiency stat. It starts at 0.00% but with each time you use the Battle Stance (defeating an enemy or blocking), the proficiency will go up by 0.02%-0.07% or so (it is limited to 0.8% per battle). Using the Battle Stance once costs 10 AP.

0% Proficiency

 * Auto-parrying: Zack automatically parries any attack while in Battle Stance.
 * Strong attack: Zack executes a 2-hit combo and cannot be downed or stopped while performing it.
 * Enhanced Guard: Zack's guard now reduces damage by 80%, in and out of Battle Stance.
 * Necromose: Zack regains a small amount of MP and AP every time he defeats an enemy.

15% Proficiency

 * Damage Limit Break: Allows you to deal more than 9,999 damage with any attack or Command Materia when in Battle Stance.

Ways to increase proficiency

 * Defeating an enemy with a strong attack while in Battle Stance (up to 31.6%)
 * Defeat an enemy with a Command Materia while in Battle Stance (up to 31.6%)
 * Block damage while in Battle Stance (up to 31.6%)