Thunder Boost

Thunder Boost is an ability from Kingdom Hearts II that raises the effectiveness of the Thunder Spell and thunder-based attacks in general. Sora, Donald and other members of your party can learn this ability. The Photon Debugger Keyblade also utilizes this ability.

Sora
Sora learns this ability from leveling up. When you learn it is based on which weapon you choose at the beginning of the game. This is when Roxas chooses from the Sword, Staff, or Shield.
 * Sword: Level 53
 * Shield: Level 99
 * Staff: Level 41

Donald
Donald learns this ability after accessing the DTD in Space Paranoids.

Jack Skellington
Begins with the ability when he joins your party.

Tron
Tron learns this ability after accessing the DTD.