YOU SAID:

My uncle cut a cat's neck until it decapitated

INTO JAPANESE

私の叔父は猫の首を切断して首を切断しました

BACK INTO ENGLISH

My uncle decapitated the cat by decapitating it.

INTO JAPANESE

私の叔父は猫の首を切って殺しました。

BACK INTO ENGLISH

My uncle killed the cat by decapitating it.

INTO JAPANESE

私の叔父は猫の首を切って殺した。

BACK INTO ENGLISH

My uncle killed the cat by decapitating it.