Crusher

Crushers are large obstacles that have made recurring appearances in Sonic the Hedgehog series. Crushers do not have any specific appearance and can be anything from moving or falling platforms, with or without spikes on them, pillars that are a part of the Zone's environment or moving blocks in the Zones. The purpose of the Crushers is to inflict an instant death on the playable character. If the crusher manages to press into a surface while the player is trapped in between the crusher and the surface at same time, it can lead to an instant loss of a life for the player, regardless of Invincibility, super transformation, shield or amount of Rings.

Adventures of Sonic the Hedgehog
One crusher appears in the episode "Lovesick Sonic", used as a backup trap for Sonic. When Sonic was knocked out by the electricity magnet, he dodged it, also saving Breezie. Scratch refers it as "The Smash Stepper".

Trivia

 * Some games have the Crusher, but the crusher only acts like a normal hazard, and only kills if one has no Rings. However, it goes through invincibility. Some people have complained when it actually made Super Sonic drop Rings.
 * Spike crusher from Marble Zone looks like one seen in Metal Man's stage in Mega Man 2, but without weight.