一撃の刃 [ichigeki no yaiba] in Japanese. It translates to 'blade of one attack'.
Final Fantasy VI
Stats: ATK 190
Equip: Shadow
Obtain: ?
Description: May randomly dispatch an enemy in one hit
Other: Can be used with Runic and Two-handed
Airborne Brigade

SSR
Type: Katana, Element: -, Growth: Slow, Cost: 31
Attack: 11,410 (lv1), 35,847 (lv200), ? (lv220), ? (lv240), ? (lv260), ? (lv280)
Defense: 11,230 (lv1), 35,280 (lv200), ? (lv220), ? (lv240), ? (lv260), ? (lv280)
Obtain: after Shattered World and Showdown, level Terra ally to 99
All the Bravest
Stats: ATK +3, From: FF6
Equip: Samurai, Ninja, Auron
Drop: Tonberry
Description: This blade kills enemies instantly in a single blow. Well, maybe not instantly.
Record Keeper

Ichigeki (VI)
Stats: ATK +79, MAG +53, ACC 95 (lv1), ? (lv5), ? (lv10), ? (lv15), ? (lv20), ? (lv25), ATK +131, MAG +80, ACC 95 (lv30)
Max Level: lv20 (initial), lv25 (first evolve), lv30 (second evolve)
Type: Dagger, Rarity: ★★★★★
Other: inflicts Death with a low probability
Other: enables use of the Shadow Fang Soul Break when equipped by Shadow
Category: Equipment