Nemeses

The farmer's nemeses were the locusts that ate his crops year after year.

The roadrunner and coyote were nemeses in the cartoon.

The scientist believed that time was the ultimate nemeses, always ticking away and limiting his ability to achieve his goals.

The cat and mouse were nemeses in the classic cartoon.

The hero and villain in the action movie were nemeses.

Writer's block and self-doubt were his nemeses when it came to writing.