From Final Fantasy Wiki

Thunder Slash as seen in Final Fantasy IX.

Thunder Blade, also known as Thunder Sword, Enthunder, and Bolt Sword, is a recurring ability in Final Fantasy. It is always a Lightning-elemental attack to one target, and is mainly attributed with the ability Spellblade.

Appearances

Final Fantasy V

Thunder Sword is a level one Spellblade that can be used by Mystic Knights. It can be used for 2 MP, and is mastered for 20 AP.

Crisis Core -Final Fantasy VII-

Thunder Blade is a Command Materia and ability in Crisis Core -Final Fantasy VII-. First Zack lifts his sword then cleaves it from left to right, dealing small physical damage and the Thunder spell to a enemy. Thunder Blade does moderate damage against Water-based enemies. It is a Level 1 Command materia.

Final Fantasy IX

There is a Sword Art that can be used by Steiner called Thunder Slash, which is supposed to deal Lightning-elemental damage equal to 19% of one target's HP, costing 24 MP, but due to a glitch, it misses almost every time. Additionally, Thunder Sword can be used by Steiner when he is paired with Vivi in a party. Thunder Slash can be learned for 30 AP by the Defender and Ragnarok.

Final Fantasy X-2

Thunder Blade, learned by Warriors, is a Lightning-elemental attack to one target. It requires 20 AP to learn and 4 MP to cast.

Final Fantasy XI

Enthunder is learned by Red Mages, which adds Thunder-elemental damage to their physical attacks.

Final Fantasy XIII

Trailers have shown Thunderblade and Shockblade as special attacks for Lightning while riding Odin in Gestalt Mode.

Final Fantasy Tactics Advance

Bolt Sword is learned by Gladiators and deals Lightning-elemental damage to one target. It is learned from the Air Blade for 200 AP, and costs 10 AP.