Instant KO

This article is about KOs that occur instantly with no launching or crossing of blast lines. For launching attacks powerful enough to KO in one hit, see One-hit KO.

Two fighters are thrown into a Danger Zone and instantly KO'd.

An instant KO is a type of KO which occurs instantaneously and in-place, without the fighter passing a blast line or being launched at all. A character suffering an instant KO will disappear into a colorful starburst explosion, then respawn as normal (or not respawn, if no stocks remain). Instant KOs were introduced as stage hazards in Super Smash Bros. Brawl, and a greater variety of attacks and conditions causing instant KOs were added in Super Smash Bros. 4 and Super Smash Bros. Ultimate. Ultimate also introduced instant variations of Screen KOs. Several instant KOs require the opponent to be at a certain damage threshold in order to be instantly KO'd, otherwise they will be launched as usual.

In Super Smash Bros. Brawl

Stage hazards

Several levels in The Subspace Emissary feature moving walls, blocks, elevators, and similar solid platforms. If the player is caught between two of these objects as they collide together, they will be crushed and instantly KO'd.
On the Pirate Ship stage, fighters can be crushed between the hull of the ship and the rock when the ship crashes into it.

In Super Smash Bros. 4

Final Smashes

If Bayonetta's Infernal Climax completes, any opponent caught by Gomorrah with 100% or more damage at the end of the attack will be instantly KO'd.

Enemies

Orne, an enemy found in Smash Run, instantly KOs fighters on contact with its Obliviate effect.

Stage hazards

Danger Zones in Smash Run instantly KO the player regardless of damage.
Danger Zones in The Great Cave Offensive damage and launch players similarly to lava; however, if the player has 100% or more damage, they will be instantly KO'd.
The interior of Master Fortress is lined with acid-like Danger Zones which cause an instant KO at or above 100% damage.
After Midgar is cleaved apart by Odin, the two halves of stage will eventually reconnect. Any fighter caught in the middle when this happens will be crushed.
When Midgar is flooded by Leviathan, opponents with 100% or more damage will be instantly KO'd if the current sweeps them into the right side of the stage.

Although Pirate Ship is a returning stage in for Wii U, the crushing hazard was removed. Players caught between the rock and the ship's hull will instead be launched and ricochet off the rock.

In Super Smash Bros. Ultimate

Playable characters' standard moves

Hero's Kamikazee will instantly KO himself when used, dealing a great deal of knockback to those near him.

Final Smashes

Bayonetta's Infernal Climax behaves as it did in Smash 4.
Bowser's Giga Bowser Punch can instantly KO fighters with 60% or more after being punched (80% when using the weaker version via FS Meter).
Zelda's Triforce of Wisdom can instantly KO fighters with 100% or more damage at the end of its animation.
Ridley's Plasma Scream can instantly KO fighters with 100% or more damage at the end of its animation.
Joker's All-Out Attack can instantly KO fighters with 115% or more damage at the end of its animation.

Items

Poké Ball summon Mimikyu will instantly KO the fighter it grabs hold of if they reach 90% damage after its attack.
Death's Scythe will instantly KO when striking a fighter at or above 80% damage with the tip of the scythe during a smash attack.

Stage hazards

Returning stage Midgar features the same crushing and flood hazards it had in Smash 4.
Returning stage The Great Cave Offensive features the same Danger Zones it had in for Wii U.
New Pork City is a returning stage with a new hazard: the bite of the Ultimate Chimera now instantly KOs fighters, instead of imparting extreme knockback as it did in Brawl.
The Red Bulborb on returning stage Distant Planet instantly KOs fighters with its bite, instead of carrying them off screen as in previous games.

Other

Ultimate is the first game in the series where Stamina Mode can be played with multiple stocks. Under these conditions, fighters who lose all HP will suffer an instant KO and respawn as long as they are not out of stocks. When the last stock is lost, the standard Stamina Mode KO occurs with the fighter falling to the ground and lying there motionless, then exploding and disappearing for good after a short pause.

Trivia

In Ultimate, if Inkling suffers an Instant KO, they do not have a standard explosion animation. Instead, as in the Splatoon games, they burst into a puddle of ink and their spirit, in the form of a squid, flies upward briefly before disappearing.