Nemeses

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

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

The computer virus was the nemeses of the company's entire network.

The hero and villain in the action movie were nemeses.

The nemeses of computer hackers are the cybersecurity experts who work to keep their networks safe.

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