An archenemy is the main enemy of someone. In fiction, it is a character who is the hero's most prominent and most-known enemy.

What does the arch in arch nemesis mean?

The word archenemy or arch-enemy originated around the mid-16th century, from the words arch- (from Greek ἄρχω archo meaning 'to lead') and enemy.

What makes someone an arch nemesis?

An Arch-Enemy, archfoe, archnemesis or simply nemesis is some character's designated and most important enemy. The Arch-Enemy can be the Big Bad, The Dragon, The Rival, an Evil Counterpart, or even a Harmless Villain. The essential element is that, with them, It's Personal.