Self-Destruct (abbreviated as SD) is when a character is KO'd without being hit by an opponent. This usually equates to a K.O such as jumping off the edge, but falls also count as SDs when the stage KOs someone. In time mode, self-destructs subtract one point by default from a player's score; this penalty can be changed to zero or two points. In bonus mode, the player's score is lowered by 500 points.
K.Oing a teammate counts as a Self-Destruct.
- The character was standing on the ground, did not get hit by anything, and fell.
- The character was hit and KO'd by a stage hazard.
In Super Smash Bros. Brawl and Super Smash Bros. for Nintendo 3DS/Wii U, however, a SD can only be attained if the KO'd character did not get hit by an opponent during the entire stock. Thusly, a character can be hit by any attack and walk off the edge, yet it does not count as an SD. Even performing a Footstool Jump without dealing damage will not make it count as an SD.
It should be noted that, in Super Smash Bros. for Nintendo 3DS/Wii U, if a character breaks his/her shield and falls down a pit, he/she will be treated as SDing, regardless of the shield being broken by either himself/herself or the opponent, unless the character has been hit before shielding (e.g. a Marth has not been hit by anything and is standing near a ledge when another Marth shows up and charges Shield Breaker. MarthA puts on his shield and MarthB' s Shield Breaker breaks the shield. MarthA is stunned and freefalls leading to a K.O. This counts as MarthA SDing, not MarthB KOing MarthA.) Also, if playing a 1-on-1 match, the person who's get a self-destruct in battle will award the opponent a point and will count as a KO in the results.