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. Most typically, the Arch-Enemy is a foil of some sort, usually a mirror foil. For example, the Arch-Enemy of the physically strong could be very smart. If there is a Greater-Scope Villain, his Arch-Enemy commonly is the Greater-Scope Paragon.

The Arch-Enemy will stand out from the Super Hero's Rogues Gallery — there will be one opponent where the relationship to the hero and the motivations for battling them are more potent. These feelings may be mutual, felt more by the villain than the hero, or occasionally vice-versa. If one side is an Unknown Rival, it won't stay that way for long.

A hero's Arch-Enemy is not necessarily the biggest threat to them. Lex Luthor is considered Superman's Arch-Enemy; Brainiac is smarter, and both Brainiac and Darkseid are vastly more powerful and dangerous, but for Lex — and, to a lesser extent, for Superman — it's personal between them. Additionally, although Superman has battled many foes of great power and strength, Luthor is still seen as his Arch-Enemy because to a general audience, he's viewed as the most iconic and recognizable of all of Superman's rogues.

Sometimes, the hero could have made the same choices as the Arch-Enemy: the Arch-Enemy is showing us what he could have become, as in the case of Batman and the Joker.

A hero may possess more than one Arch-Enemy if more than one villain from his Rogues Gallery stand out, or if a former Arch-Enemy dies and new one comes in to the picture. As an example, consider Spider-Man: the Green Goblin, Doctor Octopus, and Venom have all established themselves as recurring and iconic foes of Spider-Man, each of whom has been considered the wallcrawler's Arch-Enemy at different points in time.

Lastly, remember that this generally refers to the enemy the hero considers to be his Arch-Enemy, and ideally, it should be personal on both sides (though there are plenty of good "But for Me, It Was Tuesday"-type Arch Foes out there). Especially in the case of a Rogues Gallery, the hero is usually considered an Arch-Enemy to all of his villains, but he doesn't treat all of them as such. Electro, Rhino, Scorpion, and others all consider Spider-Man their most hated foe, but compared to the Goblin, Venom, or Doc Ock, Spidey regards these guys more like superpowered nuisances. Also, remember that being the Big Bad does not automatically make a villain the hero's Arch-Enemy. For instance, it could be that the hero's enmity with The Dragon is far more personal than the one they have with their master. It's ubiquitous enough to have its own trope: It's Personal with the Dragon. Sometimes, a villain becomes the Arch-Enemy of the hero when the villain does something that makes the hero realize that they are Beyond Redemption.

Beware of letting an Arch-Enemy fall victim to Villain Decay.

See also Breakout Villain, for those instances when a run-of-the-mill villain ascends to Arch-Enemy status.

Not to be confused with various works known as Nemesis. Also not to be confused with the Swedish melodic death metal band. Technically, the word "nemesis" originally referred to an agent of divine justice or retribution for egotistical thinking; thus Batman could be described as Joker's nemesis, but not vice versa.

Examples:

• Anime & Manga
• Comic Books
  • The DCU
  • Marvel Universe
• Films — Live-Action
  • Marvel Cinematic Universe
• Literature
• Live-Action TV
  • Arrowverse
• Professional Wrestling
• Video Games
• Webcomics
• Web Original
• Western Animation
• Other Media

Related tropes:

• Animal Nemesis: When the enemy is a non-sapient animal.
• Antagonist in Mourning: When the enemy mourns for The Hero.
• Beyond Redemption: When the hero realizes that the villain will never make a Heel–Face Turn.
• Big Bad: Usually though not always, the hero's closest enemy is often the main villain of the story as well.
• Big Bad Friend: When the hero's worst enemy turns out to have once been their good friend.
• Cain and Abel: When siblings are each other's worst enemies.
• Classic Villain: An archetypal villain who is characterized by a particular sin or vice.
• Create Your Own Hero: This villain is often the one who sets the hero on their heroic path, through their evil deeds motivating the hero to bring them down or set right what the villain did wrong.
• Create Your Own Villain: Conversely, many Arch Enemies are created by a hero's own mistakes or misdeeds.
• Driven by Envy: The villain is motivated by envy that the hero has something they don't.
• Elemental Rivalry: The hero and the villain have powers over elements that contrast in nature.
• Enemy Mine: When The Hero and his enemy work together for a common goal.
• Evil Counterpart: The enemy is the moral opposite of the hero.
• Evil Former Friend: When the arch-enemy used to be your best friend.
• Evil Versus Evil: A villain opposes another villain.
• Familial Foe: The villain is the arch-enemy to an entire family, especially if they happen to be immortal.
• Friendly Enemy: When the hero and the villain are actually relatively chummy with each other, to the point of being best frenemies.
• It's Personal with the Dragon: When The Dragon rather than the Big Bad is the arch-enemy in question.
• Joker Immunity: You want to keep the villain around to be an arch enemy.
• Luke, I Am Your Father: The villain is the hero's long lost family member.
• Nemesis Magnet: What's better than one arch enemy? Multiple!
• "Not So Different" Remark: Two enemies find out they have one thing in common. Stated In-Universe.
• Ominous Adversarial Amusement
• The Only One Allowed to Defeat You: The enemy doesn't want anyone defeating The Hero except him.
• Pick on Someone Your Own Size: The hero is a child and their enemy is an adult.
• The Resenter
• Rival Final Boss
• Rival Turned Evil: When The Rival becomes The Hero's greatest enemy.
• Rivals Team Up
• Sitcom Arch-Nemesis: The Hero and his co-worker have a petty rivalry that's Played for Laughs.
• Supervillain: The enemy of the Superhero.
• Unknown Rival: The hero doesn't acknowledge the villain as an enemy.
• Villain Takes an Interest: The villain becomes personally intrigued by the hero.
• Worthy Opponent: The villain respects the hero as an equal (or vice versa).
• Yearning for a Nemesis: When someone actually desires to have their own personal opponent.
• You Killed My Father: The hero and villain are enemies because the villain killed the hero's loved one(s).