nemesis

死敌（名词）

(noun) An unbeatable opponent that causes great harm or ruin.

EXAMPLE: The terrible winter snowstorms were the invading army's nemesis, and after seeing thousands of his brave soldiers trapped and dying in the snow, the general called for a retreat.

冬天可怕的暴风雪是入侵军队的大敌。在看到他的数以千计的勇敢战士困在雪中死去后，这位将军下令撤退。