mortal enemy
mortal foe

As we moved forward, the heat came at us like a mortal enemy.

"Then you will have offended me and made a mortal enemy."

For a moment the two men stood watching each other like mortal enemies.

But in the process, she had made a mortal enemy.

Jack had a mortal enemy and it was not a human.

But you must realize the Russian woman is our mortal enemy and will be considered as such by my men.

You may have in me a devoted friend or a mortal enemy.

But Hal knew that he had made a mortal enemy.

What went on in this bizarre meeting of two mortal enemies?

From out the night sky their mortal enemies fell upon them.