Apocalypse How/Class 2

Planetary-scale Societal Collapse. This takes an entire planet back to at least pre-industrial data, if not hunter-gatherer days. Recovery may or may not be possible.

Multiple Media

 * Generally, the more extreme portrayals of World War Three are going to have this as a minimum outcome.

Anime and Manga

 * Cowboy Bebop, in which the Gate Disaster takes out half the moon and makes Earth uninhabitable for all but the hardiest of humans. It should, however, be noted that the rest of the terraformed planets and moons in the system are okay; Earth is still in contact with the greater solar community, but is regarded as a backwater. This makes this Class 2 in theory, but it's really more a large-scale Class 0.
 * Blue Gender, in which giant bugs ravage the human population of Earth, forcing the humans into space. Admittedly, humans as a species are allowed to survive as small hunter gatherer tribes, but that still necessitates all modern civilization's knowledge and technology to be wiped out lest Gaia's Vengeance do an encore.
 * Although the Canon information is so vague as to be useless, it can be inferred that this was the result of the fall of the Silver Millennium in the Backstory of Sailor Moon -- humanity died out completely everywhere in the Solar System other than Earth, and on Earth the fall was so Egregious that the Silver Millennium and its interplanetary civilization were both completely forgotten. Exactly when this happened is uncertain, although the "thousand years ago" figure frequently bandied about is both historically improbable and the invention of the North American dub.
 * Scrapped Princess has humanity defeated and imprisoned in a medieval tech level for 5000 years. The guardian AIs have a reset option of killing off 90% if the humans get troublesome.
 * Stellvia of the Universe back-story falls half-way between this and Class 1: 99% of humans dead, global civilization mostly wiped out, yet they get right back on their feet in less then two centuries, advancing from the Stone Age to space-faring civilization. That the near-Class 2 event (the electromagnetic radiation blast from the explosion of a nearby star) is a harbinger of a Class 4 event (the arrival of the much slower physical shockwave from the same explosion) helped ensure that The Apocalypse Brings Out the Best In People. Stellvia is one of the enormous space stations built to prevent that event.
 * Tengen Toppa Gurren Lagann begins centuries after a Class 2, with humanity confined to isolated and impoverished underground villages. The nature of the cataclysm, and the surprising reasons for it, are revealed as the show goes on.
 * The world created by Tsutomu Nihei. Let's list it out:
 * In Biomega The world undergoes a large viral plague which results in odd zombification. To make matters worse, the only people left are being killed off by cyborgs and mutants, with only Artificial Humans left to protect them.
 * After that. In NOiSE. Religious fanatics are trying to bring out the chaos of the Netsphere and are doing so by doing less than humane things to people. Against them.....is a single police women who ends up not being able to stop them, and thus the Bizarrchitecture (built around the earth) begins to expand rapidly and increase the chaos. Downer Ending.
 * After that... The protagonist of Blame! is searching the the ginormous sphere for people with genes to turn off the chaos. He must deal with all the preceding crazy things mentioned (and more). Thankfully he succeeds in his mission (though the series ends right before it is directly shown).
 * After that in "Net Sphere Engineer" the last remnants of humanity are unfortunately not as safe as they would have hoped. But they have another protagonist to deal with the problems this time.
 * About 500 years prior to the beginning of Dragon Ball, a violent storm raged across the planet Namek, leaving only one Namekian on the ground and another escaped to somewhere in space. Even centuries later with asexual Namekian reproduction, there are only a few hundred Namekians left. During the Frieza saga, Frieza, his henchmen and Vegeta almost completely eradicate the Namekian race, aside from the Nameless Namekian who fled all those centuries ago, separated into the light side of Kami and the dark side of Piccolo. Piccolo becomes the only living Namekian on the surface alive prior to most of the race being resurrected by the Namekian Dragon Balls and transported by the Earth Dragon Balls, followed shortly thereafter by Namek's explosion.
 * In Heat Guy J, after humans appropriated the technology of the Celestials in their conquest for power, there were apparently large-scale wars. The result? Earth's human population is reduced to seven city-states (with some small towns and Space Amish villages surrounding them), who are mistrustful of one another and do not trade, communicate, etc. with one another.
 * In Uchuu Senkan Yamato humanity is reduced to survival in underground cites that are rapidly becoming uninhabitable due to radiation thanks to the Gamilas' continual bombing of Earth.
 * Turn a Gundam: This was the end result of the Turn A using the Moonlight Butterfly across all of the Earth's surface. The ability works by spreading nanomachines around that attack technology, turning it into sand. 2,000 years later, Earthborn humanity is barely up to early 1900s technology levels.
 * Nausicaa of the Valley of the Wind takes place a thousand years after the world has been devastated by what's implied to have been a nuclear war. The survivors have organized themselves into petty kingdoms, but are still at war with one another and technology has only progressed to the late medieval period for the most part (save for some remnants of pre-deluge technology like airplanes).

Films -- Live-Action

 * While the series started out with some aspects of civil order still around, the Mad Max films wind up here by the end.
 * The implied nuclear war happened between the first and second movie. The first took place in a Dystopia, but civilization was still intact.
 * The Matrix, which sees a machine take-over of Earth lead to most of humanity used as batteries for the evil machines.
 * The burned and depopulated world of Reign of Fire probably fits here better than Class 1, as all post-medieval technology seems to be salvaged, not anything built by survivors.
 * The Spy Who Loved Me. Big Bad Stromberg plans to start a global thermonuclear war to wipe out civilization.
 * The Terminator, another "machines kill humans" series. SkyNet nukes the Earth in 1997 (Kyle Reese's timeline) or 2004 (in Terminator 3), wiping out 3 billion humans and killing many others on sight.
 * Yor, the Hunter from the Future Aliens have literally regressed Earth back to the Stone Age. Spoony does an excellent job reviewing this campy movie.

Literature

 * In The Bible, The Great Tribulation. Exact numbers are unknown, but the description "Mortals will be rarer than the gold of Ophir," combined with Revelation detailing the fact that over half of the population will die from the war, famine, plagues and various other disasters, and most of the Christians will be beheaded, burned or starved to death, while none of the unbelievers survive Armageddon means that you could expect maybe one out of a thousand people who enter the Tribulation to come out alive, perhaps a bit more.
 * Dies The Fire and the other Emberverse books by S.M. Stirling, where a mysterious event causes all recent power sources to stop working at all (electricity, steam engines of any useful efficiency, gunpowder, etc.). About 95% of humanity dies off in the first year from starvation and lack of knowledge on how to survive in primitive conditions. Another large percentage of what's left dies off once cannibalism is no longer an option due to lack of other humans. By the end of the first book it's clear humanity is going to survive -- most remaining threat comes from would-be warlords and despots, who want to enslave rather than kill -- but the cultures that are springing up aren't precisely what you'd expect.
 * Then there's the reborn Kingdom of Britain that shows up in later volumes. It seems the U.K. military evacuated the Royals, a solid selection of reference materials, a few thousand lucky/skilled souls, etc. to the Isle of Wright and is steadily recolonizing a Britain occupied by "Brushwood Men" (and dealing with Mad King Charles and his Icelandic Queen, but that is beside the point).
 * Stirling's Peshawar Lancers accomplishes much the same thing with a series of cometary impacts that destroy industrial Europe and the eastern United States in the late 19th century, setting the stage for a Steampunk 21st century where the British Raj in India, an ascendant Japanese Empire, and the Empire of Brazil are the dominant world powers. France is a shadow of its former self and Russia.
 * George R. Stewart's novel Earth Abides depicts the near extinction of humanity from a pandemic disease. Although there are survivors, the population is too low to maintain technological advancements of modern civilization and within two or three generations humans are living as hunter-gatherers. Actually it's not as pessimistic as it sounds. Acknowledged as one of the inspirations for King's The Stand.
 * Kurt Vonnegut's Galapagos. Okay, technically the human race does survive in the end, but you can't really consider them human anymore by the time they do get back on their feet.
 * The Zombie Survival Guide dubs this a "Class 4 Outbreak" of the Zombie Apocalypse -- when there are so many zombies that humanity is overwhelmed.
 * Cell, by Stephen King. We see only US residents, and the book doesn't really address other places, but there's really no reason to think any place with cell phones was spared.
 * And of course, The Stand by the same author. King does regret not showing what the rest of the world faced, but it's clear that Captain Trips goes worldwide, especially since the US military released it into other countries so they wouldn't be able to attack us.
 * The Shannara and Knight of the Word series by Terry Brooks. Humanity nearly wipes itself out in a nuclear war, some of the survivors evolve/mutate into divergent species, magic is rediscovered, the Elves return, and the new races slowly build back up into a Medieval European Fantasy setting.
 * In Vernor Vinge's A Deepness in The Sky, every planet-bound human civilization goes through this at some point due to the limits of technology, and has been doing this for thousands of years. The Emergents manage to stave this off through Mind Control, but the true answer as of A Fire Upon the Deep seems to be to move to the parts of the galaxy where Faster-Than-Light Travel is possible. In the case of A Fire Upon the Deep, this is the answer for poor weak sophonts of human-level intelligence.
 * In The Wheel of Time series, an event occurs three thousand or so years previously known as the Breaking of the World. Caused by all male channelers going berserk, Human society is set back from near utopia to feudalism.
 * Additionally, later on in the series, it is stated that the Choeden Kal have the power to crack the world like an egg, a potential class X disaster.
 * With the  the chance of a class X disaster is averted. Granted, Rand with   can still do plenty of damage alone.
 * The Day of the Triffids by John Wyndham. The light from a meteor shower renders most of the human race blind, leaving them vulnerable to carnivorous walking plants that sting you to death and eat your corpse, and reproduce rapidly. Don't bother watching the 1962 film which conveniently has a Happy Ending when they suddenly discover that the Triffids.
 * John Varley's  Eight Nine Worlds stories, where an invasion of aliens had come to Earth and literally plowed human civilization out of existence, supposedly to benefit Earth's true higher life forms: dolphins, sperm whales and other cetaceans. At that time, humanity had one single developed colony on the moon. They were warned - once - never to land on Earth again. Four hundred years later, humanity had settled all the other 'junk' planets in the solar system. What continues to happen on Earth is a sweet mystery.
 * Nick Sagan lampshades this in Everfree, saying that it wasn't really the end of the world, because insects survived and thrived. The event itself could probably be called a 2.9 (10 surviving humans.)
 * not to mention several thousand cryogenicaly frozen people.
 * In Isaac Asimov's classic short story, "Nightfall", a planet with six suns experiences night only once every 2048 years. Each time, the darkness drives almost everyone insane and they destroy civilization. At the end the scientists are unable to convince the people of the danger and it all happens again, but they're able to save their data about the event so that the next cycle might avoid the same fate. (Of course, given that this has happened nine or ten times before, it's very much implied that all this might be for naught, as by the time the next cycle's civilization is advanced enough to understand the data, it may well have degenerated into myth.) This is the exact situation in the novel version; one of the reasons the scientists aren't believed is because it's revealed that their prediction exactly matches the apocalyptic prophecy of an ancient cult.
 * Z for Zachariah, in which World War III seems to have wiped out everything but an isolated valley in America. From the sound of it it might actually border on a Class 3, since civilization and most of the population seem to have been wiped out entirely.
 * Russel Hoban's "Riddley Walker". It's two thousand years - we think - after a nuclear war blasted everyone back to Iron Age technology. In the two millennia since the war, mankind has been getting by in a sort of neo-tribal existance, by digging up old rusting metal out of the earth to salvage the scrap metal. All history is orally related via Punch-and-Judy puppet shows and half-remembered accounts of the war are woven together with scraps of the legend of St. Eustace. And the English language is mind-blowingly different.
 * Current conditions are like this in Cthulhu's Reign, an anthology of H.P. Lovecraft-inspired After the End tales. In most stories it's a temporary condition, as events are rapidly progressing towards a Class 3a or Class 4.
 * The Wild Boy by Warren Rochelle-somewhere between this and the next, since it was unnatural means, but humanity wasn't totally extinct and was back in pre industrial mode living in the ruins (the ones not being bred by the Lindauzi anyway)

Live-Action TV

 * In a Bad Future of Heroes, the immortal Adam Munroe unleashes the Shanti virus, wiping out most of the world's population so they can build anew.
 * In the Babylon 5 episode "Deconstruction of Falling Stars", its shown that humanity all but wiped itself out in a massive civil war. It takes quite a while and the aid of the Rangers to fix that mess.
 * The plot of Battlestar Galactica -- both series -- is based on a multiple Class 2, the Cylons all but wiping out humanity's twelve planetary colonies and pursuing the pathetically small number of survivors through space.
 * With 40 missile tubes each capable of delivering eight 20-megaton kinetic kill missiles a second, the Andromeda Ascendant can destroy every population center of a Tarn Vedra (read: Earth like) class planet in under six minutes.
 * In the Star Trek: The Original Series episode "A Taste of Armageddon", Kirk threatens to use "General Order 24" which is this caused by Orbital Bombardment.
 * Babylon 5 has, as noted above, . These planet killers are more likely to be around class 2-3--one episode has Ivanova requesting atmospheric shuttles to evacuate survivors from the surface of a world devastated by the planet killer. It doesn't destroy the planet, but once it strikes, it's curtains for most of the population, and the few who remain will probably slowly die of starvation, disease, radiation poisoning, or the like unless they are rescued.
 * In Primeval the not too distant future appears to be populated entirely by giant mutant bat things that we unleashed upon ourselves. The series is non-specific if this has wiped out humanity entirely in a full Class 3a, or just mostly, but given the ferocity of the future predators and the abandoned state of cities it is at least a 2. The Big Bad does state we've wiped ourselves out, but we're not about to take a villain's word for it just yet and the series does fall on the idealistic side of the Sliding Scale so there may yet be hope. Given the geologic time-scales with which this series usually plays around, the Future Predators may not have originally played any direct role in humanity's downfall. It's just as plausible that they evolved naturally, long after we'd gone extinct, and that they would never have met humans if the Anomalies hadn't brought some into the present.
 * Doctor Who --
 * In "Gridlock", the mood drug Bliss mutated, wiping out all life on New Earth apart from the undercity of New New York which was safely quarantined by the Face of Boe.
 * The Reapers in "Father's Day" erased almost all traces of human life to fix a paradox in time, if left unchecked reaching a Class 3b.
 * In "The Parting of the Ways", the Daleks killed off every human on board the GameStation apart from Rose, and firebombed the Earth, shifting its continents, making it at least a Class 2.
 * In The End of Time,
 * In "Day of the Moon",
 * New Zealand production The Tribe had the worlds' adult population dead from an accidentally-engineered virus, and the surviving children living in a class 1 catastrophe, with mostly successful attempts to restore technology. However, in the sequel series, The New Tomorrow, set possibly some centuries later, the children's society has regressed to the point of basic small-scale agriculture, and tribes of hunter-gatherers, as well as worship of the Ancestors, and technology has all but become forgotten (some machines, still working on their own, are thought to be "monsters"), making this a pretty firm class 2.

Mythology

 * In Norse Mythology, Ragnarök would be a Class 5. However, there's one thing that makes it notable: While men, women, children, giants, animals, and monsters are wiped out during Ragnarök, two people survive, thusly allowing for an After the End scenario.

Tabletop Games

 * De Genesis, a German roleplaying game set After the End sees presumably all of civilization completely destroyed. Humanity got back to their feet, making the initial apocalypse only a Class 1 case. However, since the asteroids left some alien material that constantly expands its turf, the survival of the human race is all but probable.
 * The Great Rain of Fire, a planetary cataclysm that devastated the D&D setting of Mystara 3000-odd years ago, knocked human and elven civilization from scifi-grade technology back to savagery. The exact nature of the weapons Evergrun's elves and Blackmoor's humans threw at each other is unknown, but nukes were probably the least of them, as their conflict was so violent that it changed Mystara's axial tilt. Note that this same event rates as a Class 3a for some of the other races that were around back then, and that still others only subverted a Class 3a Apocalypse How because the Immortals preserved some of them in the Hollow World.
 * The Bliss of Bliss Stage destroyed civilization by making the earth a Teenage Wasteland.
 * The "Crucible Of God" scenario in Vampire: The Masquerade's final supplement, Gehenna, ends in this (if the PCs win), with about 90% of the Earth's humans depopulated (and corresponding numbers of most other life).
 * This is also what happens if the Garou win. You don't want to know what it'd be like if they lose.
 * Observed with regularity in Warhammer 40000. A significant number of Imperial worlds are ancient human colonies that fell into this, either independently or as part of larger-scale cataclysms and wars, then slowly worked their way back up to Stone Age or medieval-era levels over the course of thousands of years.
 * The Yozis in Exalted are trying to do this to creation, but it only falls into this category because they're not going to kill all humans. If the Yozis were to succeed it would be worse than a Class Z.
 * In Rifts, a small nuclear exchange during a major surge in the planet's magical field wiped out all human civilization, and nearly wiped out humanity itself. In the three hundred years since, small pockets of civilization have emerged here and there, but 90% of humanity lives as subsistence farmers or hunter-gatherers.

Toys

 * The Shattering in Bionicle is implied to have reduced the population of Sphereus Magna, and significantly decreased the amount of resources available, resulting in a Scavenger World where villages have to fight for supplies.

Videogames

 * Chrono Trigger, at least after the Day of Lavos. It's clear that a few isolated pockets of humanity have survived Lavos' wrath, but it's also clear that those isolated pockets are screwed, no matter how much "hope" is spread by the main characters. Luckily, the theme of the game is Time Travel...
 * The freeware game Iji begins with a vast majority of all life on the planet blown to bits, your job is to try to save the remaining life from being blown into even tinier bits.
 * By the end of Xenogears, most people either become -wels-, are absorbed into the Big Bad, are eaten by -wels-, or are killed by "angels." Only a handful of people survive, clinging to life in a couple locations. The game is supposed to have a happy ending.
 * This isn't the first time either. Several thousand years before the start of the game, the Zeboim era was a technology rich society that was done in with a combination of low birth rates and nuclear war.
 * Skies of Arcadia has a backstory that includes a Class 2, although by the time the game actually begins, enough centuries have passed that civilization has made its way back to a rough analog of steam technology with electricity in a few scattered places.
 * Might and Magic..
 * Mother 3 has an interesting variant of this, balancing between Classes 1 and 2.
 * System Shock. The delusional AI SHODAN of Citadel Station planned to destroy every major city on Earth from space to assert her (its?) godhood over the survivors. Failing that, she also tried to unleash a plague of mutagenic virus on the planet, which would turn pretty much everybody to mutant-zombies.
 * Mankind was kicked back to the stone age 3.000 years before the beginning of Arc the Lad,  you can hate the writters for this
 * Phantom Dust is a class 2 in many ways. The memory erasing dust on the surface makes long term exposure to environments that aren't pressure sealed a dangerous or even suicidal venture. The remains of humanity exist in underground shelters seemingly stitched together from collapsed subways. You only ever encounter one such lair, though it's suggested that more exist. Their government is comprised of a silent dictator and his interpreter, and their civilians/field agents are nearly all of suspect sanity. Parts of the vault seem to have technology superior to modern day tech, but the inhabitants are mostly ignorant; they have no idea how to grow crops and have to raid the surface for food and supplies. Of course, later on in the game you discover
 * The Great War in the Fallout series caused one of these. Sure, it was worse in some places than in others, but humanity's pretty much been busted back to the Stone Age. Social organization is tribal in most cases and only the New California Republic even approaches Jared Diamond's definition of a "state".
 * I Am Alive The entire world is massively FUBAR by some unknown cataclysm. The player must navigate the shattered, devastated ruins of what was once New York in order to find his daughter and girlfriend.
 * I Am Alive The entire world is massively FUBAR by some unknown cataclysm. The player must navigate the shattered, devastated ruins of what was once New York in order to find his daughter and girlfriend.

Webcomics

 * In The Inexplicable Adventures of Bob, the dragons did this to themselves with an "iridium bomb," wiping out the dinosaurs in the process. All because they panicked during a clumsy First Contact.
 * One of these appears in the backstory of Wapsi Square. Thousands of years before the comic starts, an ancient civilization tried to create the ultimate weapon. Predictably, they lost control and it destroyed most of the world. The three parts of the weapon are now main characters.

Web Originals
"Time Traveler: "In the year 2258 the World Goes to War and with our level of technology, almost everything is destroyed. Billions die, entire nations vanish in fire, it’s a world we cannot afford to let happen.”"
 * Tech Infantry had the Exodus spin-off project, where a much larger catastrophe wiped out most life in the galaxy, and one planet worth of survivors quickly lost most of their high technology and regressed to a Medieval stage of civilization.
 * The entire reason why the time traveler in the United States of Ameriwank visited George Washington in the first place.

Western Animation

 * This was actually the ending to the last cartoon of the "future trilogy" Tom and Jerry cartoons from the Chuck Jones run.

Real Life

 * The Toba Catastrophe is an event that may have happened about 75 thousand years ago, when a supervolcano reduced human population to 10,000 individuals total. There's a lot of tantalizing evidence that this may have happened, but no absolute proof.
 * Mass Extinction-level events would certainly count as high-level class 2's; events such as the Cretaceous-Tertiary (K-T) event, which among others killed off the dinosaurs. Or the great extinction event ever, which was the Permian-Triassic event, which killed off approximately 90-95% of all life on earth. It's not for nothing that archaeologists, who aren't a profession usually given to mass hyperbole, refer to it as The Great Dying.