Many cultures have the idea of an eternally recurring evil. A Timeless Archenemy. The Eternal Cultural Adversary. A Satanic Archetype. A God of Evil. Not an Orcus on His Throne, just a villain who keeps coming back for more. Maybe it's one baddie with multiple identities racking up an endless Historical Rap Sheet. Either they're immortal, or there's an element of returning from being apparently dead or seeming way too old to fight to keep the conflict going ad infinitum. The reason both are included is that this trope is as old as mythology, and in its early era the concepts of The Ageless, resurrection, and absurd longevity were fairly interchangeable. Sometimes the character exists because As Long as There is Evil in the world, they will never go away becoming an Ancient Evil in the process. Maybe the The World Is Always Doomed because Evil Evolves and changes to survive and cause malice throughout time. Perhaps they exist to fulfill some concept of Balance of Good and Evil in the setting. Whatever the reason, this baddie will not stay down forever and will return in some shape or form to cause trouble for the good guys once again.
Likely the heroes of each generation must fight and defeat the Eternal Villain because Evil Only Has to Win Once for everything to fall apart. Often the villain must be put into some form of Sealed Evil in a Can to keep it at bay, but it will be back sooner or later. A diametric contrast to the Eternal Hero and sometimes the force of malice or opposition the hero must fight against in various stories as an Evil Counterpart.
- All for One from My Hero Academia has been the setting's Symbol of Evil and the Big Bad to every user of One for All, from the first wielder of One for All, his younger brother, all the way to Deku himself. Many efforts of wielders of One for All across time have been spent trying to accumulate enough power to take him down for good, and not one has succeeded as of yet and a number of them have died at All for One's hands.
- In the Sailor Moon manga storyline, Chaos is this, as the source of all evil in the galaxy and orchestrator of all of the bad stuff that happens over the course of the series. Queen Metalia, Death Phantom, Pharaoh 90 and Queen Nehellenia (or Nehellenia's cursed mirror in the 90s anime version) were nothing more than embodiments of its will and it is the entity pulling Sailor Galaxia's strings for much of the story. Sailor Senshi exist across the galaxy and have all been engaged in an epic battle against Chaos. Even after being defeated by Sailor Moon, Chaos has survived, and one day it'll be back to likely fight against the Sailor Senshi for eternity until it finally wins.
- DC Comics Vandal Savage is one for the DC Comic hero community. He was once a vicious Cro-Magnon caveman who gained immortality and spent the next thousands of years maintaining a variety of villainous identities in concert with several historical figures to conflict with several heroic figures. He also made living claims that he was murderous figures such as the pirate Blackbeard, Genghis Khan and Jack the Ripper. At many points he was foiled by his nemesis, the Immortal Man or another virtuous warrior, but always returns to cause trouble again. Best exemplified by his own Badass Boast after living to the 853rd century:
Vandal Savage from DC One Million: "Send me your superheroes from past, present OR future. I'll kill all of them."
- Tiamat from the Dark Gods is an ancient force of evil that has been the underlying source of malice for every supernatural horror in human history. It has constantly done battle in many different forms of the Mythological Serpent to combat Murdock, an immortalized Contemporary Caveman imbued with mystical power who took on various God Guises across history to fight it (i.e. Thor vs Jormungand, Osiris vs Apep, Zeus vs. Typhon, etc.) The trope ends up turned on its head into Evil vs. Evil considering despite Murdock's saintly moments, he's a strong tyrannical case of Order Is Not Good, despite fighting a worse evil.
- In Valiant Comics, the Immortal Enemy also known as Mr. Flay would be an example. Mr. Flay is a monster created from the Earth that is reborn every age to hunt and kill Geomancers, representatives chosen by Mother Earth to protect the planet, and it takes on the form of each age's collective fears. The Immortal Enemy continuously does battle with the Eternal Warrior aka Gilad Anni-Padda who acts as the protector of each Geomancer. The Immortal Enemy has succeeded three times, marking Gilad with a scar each time. After each time a Geomancer is killed it marks the fall of a civilization, only for the Immortal Enemy to rest and rise again when another Geomancer reveals itself.
- The DC Extended Universe has a few:
- Ares from Wonder Woman (2017) defended the Earth from Apokoliptian invaders, only to later turn on his brethren and spend the next millennia hiding amongst humanity and seducing them towards warfare and evil. Ares would resurface during the Great War to kickstart his grand finale to end humanity, where he'd meet his demise at Wonder Woman's hands.
- Darkseid in Zack Snyder's Justice League led the above-mentioned invasion of Earth thousands of years ago and spent millennia ever since subjugating worlds. His likeness would appear in at least two works of art as a figure of great evil.
- Wonder Woman 1984 the God of Lies and his weapon - the Dreamstone - have appeared at random points in history to unrelated civilizations with the promise of granting wishes, only to bring about ruin through humanity's own selfishness. The Dreamstone was last sighted in 1984, while the God of Lies remains unconfirmed.
- Ganondorf from the The Legend of Zelda is essentially one to Link's Eternal Hero. This ties back into Skyward Sword, where the original Demon King, Demise, cursed the royal family of what would become Hyrule and its chosen hero to be forever haunted by an incarnation of his hatred. This evil took the form of Ganondorf and as part of the curse he has lived to become an ancient, eternally reincarnating embodiment of an even older evil that eternally returns to bring ruin to Hyrule every time he shows up until Link and Zelda defeat him.
Demise: My hate... never perishes. It is born anew in a cycle with no end! I will rise again! Those like you... those who share the blood of the goddess and the spirit of the hero... They are eternally bound to this curse. An incarnation of my hatred shall ever follow your kind, dooming them to wander a blood-soaked sea of darkness for all time
- Sigma is essentially one for the Mega Man X series. He swore to always return so long as X and Zero exist to torment them and slaughter humanity, and that promise has certainly stuck one way or another. In X8, Sigma seemed to finally acknowledge his increasing body decay and limited time, so he hijacked the production of New Generation Reploids to instill his personal data across all of them except for Axl. While Sigma's next stand appeared to have finally been his last, it didn't matter, because he effectively created an entire line of Sigmas to succeed him. Even proclaimed by himself in Megaman X7.
Zero: You never give up, do you? Even when we break you down to scraps, you always come back.
Sigma: That's right, folks! I'll do it again and again! I will make X and Zero mine! Now come and get me! Give me a good fight! Like you always do!
- Clockwork from Sly Cooper is one to the Cooper Clan and their allies. He's an ancient criminal owl who use the Power Of Hate and cybernetics to live thousands of years just to get his revenge on the Cooper Clan for besting him in thievery. As such, he has spent generations in conflict with and killing members of the Cooper Clan, always returning to haunt the next generation.
- Dracula from the Castlevania franchise is essentially this as the overarching force of evil that must always be defeated. After his wife was burned at the stake for practicing medicine, Dracula snapped and decided to wage war against the world and God Himself, constantly forced into battle with the Belmont Clan (with assistance from the Morris and Belnades families on occasion) who have thwarted his undead armies every generation. His reign as the lord of Castlevania finally came to an end in the year 1999, when an alliance of various world armies, aided by the Catholic Church and the Hakuba Shinto shrine, succeeded in sealing Dracula away from his castle (the source of his power), with Julius Belmont finishing him off, but he is reincarnated as Soma Cruz, and he always finds a way to come back to continue where he left off, no matter what.
- Garland from Dissidia Final Fantasy is essentially one as a Blood Knight and The Fatalist, having been a prisoner of the cycles of war against the heroic Warriors of Cosmos summoned by the Gods and his timeless enemy the Warrior of Light, since they began and knows he will inevitably be caught in a time loop in his home world. As far as he's concerned, everything is predestined to happen and the other fighters in the war should accept their fates.
Garland: As the conflict between the Gods carries on for all eternity, so our battles will be repeated. Forever and Ever!
- In Final Fantasy X Sin is this as a cyclic calamity form of this trope. Sin is a ginormous whale-like monster who periodically ravages the coasts of Spira and has done so since time immemorial. Brave Summoners are regularly charged with sacrificing their lives to conjure a Final Aeon to keep it at bay until it springs up again (the last such period, known as the Great Calm, lasted all of ten years), with the Yevonite religion believing Yu Yevon first came up with the ritual with the aid of his daughter Yunalesca. As the game progresses, we learn that Sin is in fact a defense mechanism from a long-ago war that actually enforces Medieval Stasis by destroying towns above a limited level of technology, and that Sin continuously returning was the deliberate goal of Yunalesca and Yevon. The end goal becomes to defeat Sin without resorting to the Final Aeon technique by killing Yu Yevon himself, who's become a questionably-sentient floating glyph piloting Sin who only recognizes that he needs to destroy technology.
- Happens in the case of HABIT in Every Man Hybrid. In later videos, it's revealed that HABIT hasn't just tormented the boys during their loops, but has been tormenting them and their reincarnations since at least the '70s. Given that HABIT is an immortal body-hopper, he's been around long enough to exist in every cycle the boys go through in some shape or form.
- The Lich from Adventure Time is this trope to many versions of hero in the show, born from the comet that destroyed the dinosaurs which was attacked by the heroic Ice Elemental Evergreen and the force of malice that destroyed the world during the Mushroom War. He eventually fought and was sealed away by one of the Precursor Heroes Billy before getting free and entering conflict with Finn. He eventually spread across the Multiverse, and becomes a constant defeated enemy of the Finns of the Multiverse.
- Apocalypse, like his comic namesake, from X-Men: The Animated Series is presented as this, having been described as a force of evil across generations that has brought civilizations to ruin. Each time, he comes into combat with those who would combat his evil and be warded away, and continue once again. He actually lampshades this when fighting Cable and appears to have a minor Villainous BSoD upon realizing he may not be able to ever truly win, no matter how many heroes he fights. This changes when he realizes he now has Time Master powers and opts for a final gambit to remake the world so he will never lose again.
Apocalypse: Is it possible you are correct, mutant? I have been battling your kind for thousands of years. I should have triumphed long ago! But what if, like tortured Sisyphus, I cannot win? Ever! What a cruel joke! Am I doomed to struggle with such filth until the end of time?!
- Thunder Cats:
- Mumm-Ra has been the evil overlord of Third Earth for generations prior to the arrival of the Thundercats, having been active ever since the place was First Earth.
- This antagonist status becomes even more personal in Thundercats 2011 where Mumm-Ra was the original master of ancestors of the Uplifted Animal Races that make up the cast and has been an enemy of the cats (with the exception of the tigers) since Leo, Lion-O ancestor's, overthrew him and returned to plague Leo's descendants personally out of spite.
- In Mighty Max, Skullmaster has been trying to conquer the world and enslave humanity ever since the time of Atlantis, which he personally sunk. He has been opposed throughout history by a succession of heroes holding the mantle of The Mighty One, with one managing to trap him in the Earth's core. In fact, many of the one off villains are actually ancient evils that have be-devilled mankind and its various protectors throughout history, which the title character must put an end to.
- In Superman: The Animated Series, while being consummately "evil" may be debatable, the fifth dimensional imp Mr. Mxyzptlk claims he's been beguiling heroes with his weird games and nonsensical pranks for generations, either thwarted or leaving on his own to torment the next goody-goody who gets on his nerves.