A one-hit KO (abbreviated OHKO), also known as hit KO or hit kill is an attack in Super Smash Flash 2 which, as the name suggests, KO's opponents in one hit when their damage 0% and if the victim's flight path is not obstructed. As such, they are very powerful moves and most have to be charged. Self-destructs do not count as OHKOs. In order to acknowledge the attack was a OHKO, it has to share the following restrictions:
- The opponent does not tech, DI, or momentum cancel.
- Knockback may be insufficient to KO at 0% on very large stages (e.g. Temple, Devil's Machine, Crateria).
- Knockback may be insufficient to KO at 0% if the attack had been landed previously (due to stale-move negation).
- The opponent and user do not have any modifiers such as being giant, tiny or metal.
- The damage ratio is set to 1.0 with no handicaps.
In Super Smash Flash, there are no OHKO attacks, as hitboxes have a constant, per-frame damage output rather than a single set value. However, instant-KO attacks are commonly erroneously referred to as OHKOs regardless.
- Home-Run Bat's smash attack.
- Jigglypuff's Puff Up at the moment it utters its name and begins deflating, it has an abnormally large hitbox.
- Captain Falcon's Blue Falcon.
- Marth's Critical Hit.
- Black Mage's Random Encounter at the moment it conjures the "Flare" spell on the screen.
- The Cherish Ball in Event #36: Gotta Cherish Them All.
- Thwomp from Bowser's Castle.