A crush is a very uncommon method of being KOed, which involves the player's character being stuck between two solid platforms that move into each other; if the player is unable to move out of the way from the common collision point of the two platforms, then they will be crushed when the two platforms meet. This results in an instant KO regardless of the player's accumulated damage.
In Brawl, crushing is a specific property of the code for moving objects, meaning it does not have a hitbox and cannot be prevented through invincibility (such as the Super Star item). It is also coded to only occur in The Subspace Emissary; regular stages cannot crush by any means. In Smash 4 onwards, the effect of crushing on stages is caused by a special hitbox generated by the stage, and as such can be prevented through invincibility. No object in Stage Builder is coded to have a crushing hitbox.
Stages that can crush
On Midgar, summoning Odin via Summon Materia on the stage will cause him to slice the stage in half. After some time, the two halves of the stage will come back together; players caught in between these two halves will be crushed.
In Ultimate, on Distant Planet, when the Red Bulborb swallows a fighter, they will be crushed when its mouth closes. This did not occur in Brawl and for 3DS, where instead the fighter would be trapped inside and carried offscreen for a guaranteed KO.
In The Subspace Emissary
The Subspace Emissary features several stages with crushes in them; owing to the mode's focus on platforming, the player is tasked with correctly timing their movements as to avoid these crushes. The following stages have crushes:
- The Plain: By the moving walls when they rise up from the ground.
- The Cave: By numerous rising and dropping rock pillars, and the section of gapped moving rock walls.
- Battleship Halberd Exterior: By the pillar door opened by the button when it closes again, and by the metal walls that enclose on the door to the outside of the Halberd.
- The Wilds (Part II): By the elevator, the spike platforms as they rise up to the ceiling, and by enclosing rock walls towards the end of the level.
- The Path to the Ruins: By the two elevators as they go back down.
- The Ruins: By any of the elevators, the rising and falling platforms and walls, the falling spiked platforms as they go back up, and by the opening and closing metal pillar doors.
- The Research Facility (Part I): By the elevator at the start of the level.
- The Research Facility (Part II): As seen in the above GIF, and by the similarly designed rising and falling box platforms.
- The Subspace Bomb Factory (Part I): By the elevator.
- The Subspace Bomb Factory (Part II): By the falling spiked pillar activated by the red switch, the enclosing walls just before the section that triggers the R.O.B reveal cutscene, and the rising platforms just before the Meta Ridley fight.
- The Glacial Peak: By the spike stone pillar in the trap room, and the moving ice pillars.
- The Great Maze: In all the respective locations listed above that appear in the maze.
- Due to crushing being caused by a special hitbox from Smash 4 onwards, it is theoretically possible for a fighter to get crushed even if they are not necessarily in between the two crushing objects, as long as the fighter's hurtbox somehow overlaps with the hitbox. For example, a Giant Donkey Kong crouching on Midgar can touch its crushing hitbox even while grounded on the stage. Similarly, the Distant Planet Bulborb's crushing hitbox is created about 11 frames before the mouth actually closes.