One-hit knockout move

One-hit knockout moves (Japanese: 一撃必殺わざ one-hit knockout move), commonly abbreviated as one-hit KO moves or OHKO moves, are moves whose effect is to immediately drop the target's HP to zero. When such a move successfully hits, the game will display the message "It's a one-hit KO!" (or simply "One-hit KO!" in Generation I).

All OHKO moves have a base PP of 5. If an OHKO move becomes a Z-Move, it will have a power of 180.

A Pokémon with the Ability Sturdy will be unaffected by OHKO moves, unless that Ability is negated (such as through Mold Breaker or Gastro Acid). A Pokémon with Wonder Guard is also immune unless it is weak to the type of the OHKO move. At full HP, a Pokémon holding a Focus Sash will instead be reduced to 1 HP by any OHKO move.

In the Pokémon Mystery Dungeon series of games, OHKO moves can hit regardless of level, although they are very prone to missing as always. When one hits, the game states that the target fainted through "calamitous damage" (changed to the standard "It's a one-hit KO!" in Gates to Infinity). However, they actually do 9999 damage, which can be seen when the attacks are reflected by IQ skills such as Counter Hitter if the Pokémon is revived by a Reviver Seed.

Accuracy mechanics

Generation I

All OHKO moves have an accuracy of 30%, but they will automatically fail if the user's Speed stat is lower than the target's. An X Accuracy will guarantee that all OHKO moves hit. The accuracy of OHKO moves in Generation I is affected by the standard accuracy and evasion stats.

Generation II

OHKO moves automatically fail if the target has a higher level than the user. Their accuracy starts at 76/256 (approximately 30%) and increases by 2/256 (approximately 0.8%) for each level the user is above the target. This means that if the user's level is 90 levels greater than the target's, the move will have 100% accuracy. An X Accuracy will guarantee that all OHKO moves hit. The accuracy of OHKO moves in Generation II is affected by the standard accuracy and evasion stats.^[1]

Generation III onward

OHKO moves automatically fail if the target has a higher level than the user. Their accuracy starts at 30% and increases by 1% for each level the user is above the target. Accuracy and evasion stats no longer influence the move's accuracy, including modifiers from items such as Wide Lens or Abilities such as Compound Eyes. Effects that allow moves to always hit (such as No Guard or Lock-On) still work on OHKO moves.

In Generation VII, the accuracy of Sheer Cold is lowered if the user is not an Ice-type Pokémon. In addition, all OHKO moves now display their accuracy as 30% instead of —; the working accuracy is still calculated by the same formula, however.

List of moves

Fissure	Guillotine
Ground	Normal

Horn Drill	Sheer Cold
Normal	Ice

Trivia

• Starting in Generation III, type-effectiveness messages no longer appear with the successful use of a one-hit KO move.
• Lapras can learn the most one-hit KO moves of any Pokémon (excluding Smeargle), being able to learn Sheer Cold, Fissure, and Horn Drill.
• All one-hit KO moves are normally ineffective against a type of Pokémon. Fissure cannot affect Flying-type Pokémon, Guillotine and Horn Drill cannot affect Ghost-type Pokémon, and Sheer Cold cannot affect Ice-type Pokémon (as of Generation VII). Of these, only Sheer Cold's ineffectiveness is not based on a type immunity, and thus cannot be bypassed (e.g. with a move like Gravity or Foresight). Sheer Cold is also the only one-hit KO move where this ineffectiveness did not exist until after its debut generation.
• Starting in Generation VII, Sheer Cold is the only one-hit KO move to potentially have different accuracy mechanics compared to all other one-hit KO moves.

References

This article is part of Project Moves and Abilities, a Bulbapedia project that aims to write comprehensive articles on two related aspects of the Pokémon games.