Oxygen Destroyer

From Wikizilla

The Oxygen Destroyer was a fictional weapon of mass destruction used to kill Godzilla in the original 1954 film. It was the invention of Dr. Daisuke Serizawa, who feared the power of the weapon and in the end of the film, killed himself when detonating it underwater to kill Godzilla.

The weapon was first demonstrated on a tank of fish, which it instantly reduced to skeletons. When it was used on Godzilla, though, it appeared to destroy the entire creature, bones and all. However, in Godzilla Against Mechagodzilla, Kiryu's blueprints incorporated Godzilla's skeleton within him to make the design process and construction less strenuous.

The Oxygen Destroyer was later revealed to have awoken prehistoric creatures that mutated into the monster Destoroyah in the 1995 film Godzilla vs. Destoroyah. That film also noted that "if it had've been used on the ground, it's quite obvious that Tokyo would've become a cemetery."

The chemical reaction initiated by the weapon (which is the actual part that destroys the oxygen) also powers one of Destroyah's attacks, a beam of micro-oxygen, in the shape of a double-helix, with the destructive power of the Oxygen Destroyer itself.