Deluge

Deluge (大洪水) is a recurring Water-elemental ability in the Final Fantasy series.

Final Fantasy IV
Deluge (known as Big Wave in the SNES release and Tidal Wave in the GBA release) deals damage equal to 25% of the target's maximum HP; contrary to popular belief, it is non-elemental. In the DS version, Deluge is instead a strong Water-elemental ability. It is used by Leviathan, Cagnazzo (as part of the Giant of Babil gauntlet), Ogopogo, and Lunar Leviathan.

Final Fantasy IV: The After Years
Deluge reverts to its GBA name of Tidal Wave; here, it is simply a strong non-elemental attack. It is used by Leviathan and Orthros.

Final Fantasy V
The Predict command of the Oracle can randomly cast Deluge, which deals Water damage and inflicts Toad to either the party or enemies.

Final Fantasy X-2
Deluge can be used by Kogoro, Yuna's pet in the Trainer Dressphere. It inflicts Water-elemental physical damage and may also cause Sleep.

Final Fantasy Tactics Advance
The Chill Rod teaches the Illusionist Deluge for 300 AP. The attack deals Water damage to all foes simultaneously and costs 32 MP to cast. It is stealable through the ability Steal: Ability, is also susceptible to Absorb MP, and has a Magic Power of 17.

Final Fantasy Tactics A2: Grimoire of the Rift
Deluge is again learned through the Chill Rod by Illusionists, but now requires only 250 AP to master and 28 MP to cast. Its effects are the same as before.

Dissidia Final Fantasy
Deluge is the summon attack of Cagnazzo. Twenty seconds after Cagnazzo is summoned, Deluge switches the Brave of both characters.