We often see these words used interchangeably, but there are some subtle differences between them. An enemy is a foe who’s hostile toward the protagonist (or central character) of a story. A nemesis, meanwhile, is an opponent or rival whom a protagonist can’t overcome.

The Enemy

In literature, an enemy is often referred to as an antagonist or a villain. This character is typically hostile toward the protagonist. They want to keep the protagonist from achieving a goal.

Sometimes you’ll also hear enemy used to refer to an armed foe, an opposing military force, or a hostile nation or state. This tends to pop up a lot in political discussions.

— The Archenemy

In comes the associated derivative — archenemy. In literature, as well as in comic books and movies, an archenemy is a supreme enemy. Conflict with an archenemy is always personal. You probably have a history with your archenemy. If you have an archenemy, the implication is that you have other, lesser enemies as well.

The Nemesis

Your nemesis is a far more intimidating figure than either an enemy or an archenemy. Enemies may come and go, but your nemesis is a more-or-less permanent fixture in your life. A nemesis pursues you relentlessly, often in search of vengeance. In fact, the word nemesis is comes from the Greek word némesis meaning a dealing out. This word comes from the verb némein meaning to dispense justice. The Greek goddess Nemesis was the goddess of divine retribution. She was also known as Adrasteia, meaning the inescapable.

A nemesis typically holds some degree of fascination for a protagonist, and vice versa. They’re an antagonist who’s bent on revenge, who doesn’t go away, and who seems to haunt the mind of the protagonist. They’ve moved past being an enemy to become something much more personal.

— dictionary.com