Shock (ability)

Shock is a recurring ability or spell from the series. While the spell "Shock" would allude to a Thunder-elemental spell, it's more often than not a non-elemental spell, the only exclusion being Final Fantasy XI. It is also, when used as an ability, been associated with the Warrior class.

Final Fantasy IV: The After Years
Shock is one of Edge's new Ninjutsu skills. It does Lightning-elemental damage to one or more enemies.

Final Fantasy VI
Shock is the special command ability of General Leo Cristophe and the Retainer Rage. It deals large amounts of non-elemental magic damage to all enemies.

Final Fantasy IX
Shock first appears as one of General Beatrix's abilities. Later in the game, Adelbert Steiner can learn it as a Sword Art from the Ragnarok. It deals large amounts of physical damage, roughly three times the damage Steiner's normal attack does.

Final Fantasy XI
Shock is a Lightning-elemental Black Magic spell. It inflicts Sap and reduces the target's MND stat.

Final Fantasy XII
Shock is a Black Magick spell which inflicts heavy non-elemental damage on a single target. It is available on Black Magick License 6 costing 50 LP. The spell can be purchased at Balfonheim Port for 9,400 gil and initially uses 34 MP to cast.

The International Zodiac Job System listed Shock as a Black Magick 11 License. It is bought in Balfonheim for 7,800 gil and consumes 34 MP. Only the Job class Black Mage can use Shock.

Final Fantasy Tactics
Beowulf's Shock! acts like the Lifebreak spell.

Etymology
In this case, Shock refers to a dangerous condition that disrupts the blood flow of the body.