Cloud: I couldn't finish 'em. Looks like this's gonna get complicated.
The following tables are incomplete and require the specify if an attack sets HP to one, or does damage to lower HP to one. entries to be filled. If you wish, please examine the table and add anything missing. Remove this notice upon completion.
HP to one abilities reduce the target's HP of one regardless of their current HP. This is sometimes done by simply setting the targets to one HP, at other times by inflicting damage to them equal to their max HP minus one. They are commonly used by final bosses and superbosses. One of the best known of these abilities is Heartless Angel, which has become the trademark attack of Sephiroth.
Omega Weapon has a similar ability called Megiddo Flame. The ability does not reduce the party to one HP, but deals a guaranteed 9,998 damage to the entire party, and thus the only way to survive is to have 9,999 HP, leaving the party with one HP after the attack hits.
Diving into the game code reveals two dummied spells specific to Selphie, Percent (a reduce-HP-to-1 move similar to Matra Magic), and Catastrophe (major damage to all enemies). These two spells were removed from Selphie's spell list in the final build of Final Fantasy VIII, but can be found via third-party data exploitation programs, although they just use Fire's spell animation.
Beatrix uses Stock Break and Climhazzard to reduce the party's HP to 1 when fought as a boss, and these abilities cannot be blocked or avoided. This ends the battle. When these abilities are used by the player's party, Stock Break and Climhazzard instead simply deal major non-elemental damage to all enemies.
Fall damage from a high enough point will leave your character with no less than 1 HP as long as they are not currently targeted by an enemy. In the case of being targeted by enemies, falls that would normally leave your character at 1 HP will instead prove fatal.
Reduces HP to 1 and inflicts Incurable, which prevents healing. The higher the target's HP at the time of being reduced to 1, the lower the duration of Incurable
Kefka
Cleansing Strike
Entire alliance
Reduces HP to 1 and inflicts Doom, requiring a full heal in 15s to avoid death
Inflicts damage that reduces HP to triple digits. Inflicts Doom on Healers and Tanks requiring a full heal in 10s to avoid death, and Beyond Death on DPS requiring them to take lethal damage within 10s to avoid death
Shango uses Divine Storm to reduce the party's HP to 1 when fought for the first time. This leads to the end of battle once he has used it. The same goes for Glacial Dance used by Cocytus. The battle are scripted events when these are used. When these abilities are later used by them during their real battle, they deal normal damage.
Incurable, which prevents healing. The higher the target's HP at the time of being reduced to 1, the lower the duration of Incurable
Doom, requiring a full heal in 15s to avoid death
Blue Mages
Superbolide, rendering immune to damage for 8s
Gunbreakers
Beyond Death on DPS requiring them to take lethal damage within 10s to avoid death
True Walking Dead, requiring a full heal in 15s to avoid death
