Apocalypse How/Class 6

Planetary-scale Total Extinction of all life of any kind. The planet is left as a lifeless husk.

Anime and Manga

 * In Puella Magi Madoka Magica, this is how.
 * This is what ultimately happens to the world in Wolf's Rain. That is,
 * In Heartcatch Precure, the main Big Bad Dune does this after defeating the heroines, restoring his full powers, reducing the Great Heart Tree to a withered husk and unleashing his Desert Devils on the Earth, reducing it to a lifeless desert. Thankfully,

Comicbooks

 * Long before Malefic rolled around, General Blanx did this to Mars in the 1969 Justice League of America & Martian Manhunter story "And So My World Ends," setting the entire planet on fire with an ever burning Blue Flame that consumed everything down to the bed rock.
 * The ultimate consequences of Bishop's actions (and sundry unrelated disasters) in the bad future in Cable and X-Force qualifies as this grade of Apocalypse How (either that or a Class 5). Let's see--he stole a number of WMDs. One of them nuked Australia. Another turned South America into a perpetual conflagration. Nerve gas or something like it released in Beijing depopulated Asia. Africa's fate is uncertain. The fifth of them destroyed Europe's fresh water. The sixth was used against Cyclops when X-Force captured him and brought him to San Fran or Utopia in the Present. In response to one or more of the first five (they all happened in different years), the remains of future-UN declared open colonization on North America. In retaliation, the remains of future-US's government and military turned themselves into roach-people. Cue genocidal war (Cable volume 2 issue 9 or thereabouts). North America was ruined. It had recovered a little by the end of the 30th Century, at least around NYC and up into the Adirondacks a little (Cable and X-Force crossover Messiah War, when Hope was about 9). But, by the 3120s (later issues of Cable), even there, the planet was dying (storms of blood). And what did Bishop have done to him? Cable or Hope (who was by that time about 16) scrambled his time-travel device and sent him to 6900 AD or so in that timeline. That possible future Earth was basically utterly dead. Nice Job Breaking It, Villain.
 * This strip from Argentinian cartoonist Quino.
 * Nekron's plan involves a mixture of this and Class X-4: by killing the Entity, the result would be a simultaneous death of every living thing in the universe.

Literature

 * The Star Wars Expanded Universe has the Republic, Separatist, and Imperial Order Base Delta Zero, an orbital bombardment which comes in two main flavors. The quick and dirty version is a class 3a that involves destroying all cities, industrial assets, infrastructure and people, and can be executed by handful of Star Destroyers in a single day barring resistance and may include surface landings to conduct mop-up operations. The second variant is class 6, frequently cited as calling for a fleet of ships to melt the planet's crust to a depth of 1 meter. Ultimately, how much it falls between these two categories depends on how many fleet assets are available, how pressed for time the commander in charge is, and how vindictive he is feeling when carrying out the order.
 * Hyperion - The Pax orders this being done to the Ousters. A Hegemony officer predicts the Ousters are going to do this to a planet, although there is no evidence they ever did.
 * Peter F. Hamilton's Nights Dawn trilogy contains a planet called Garissa. Or rather, did. It was sterilised with antimatter-fueled "planet busters". In effect, they caused planet-wide radioactive hurricanes that would rage for centuries.
 * Iar Elterrus' Burden of the Emperor describes the summoning of an Eldritch Abomination roughly described as the embodiment of void or nothing. A successful summoning would wipe out all life, and there is no way to know if the planet would survive the ordeal, placing this on top of class 6 bordering class X-1. As of the third book,
 * Valentin Ivashchenko's Warrior and Mage series feature the Fallen God seeking for a way to reenter the world. Said reentry would possibly destroy the world and surely wipe out life, placing this between class 6 and class X-1. Mages in danger of becoming one of those reentry points (usually necromancers under great stress and catastrophic circumstances) are handled with extreme prejudice.
 * Vadim Kazakov's Measure of Chaos series features a "Well of Chaos" corrupting the land. The corrupted area is quarantined by mages and special multinational armies. A breach in the quarantine will wipe out life, replacing it with chaos-spawned things.
 * In H.P. Lovecraft's sonnet "Fungi From Yuggoth", Nyarlathotep brings about the end of the world, descibed as "crushing what he chansed to mould in play, the Idiot Chaos blew Earth's dust away". That's pretty vague, but seeing as "Idiot Chaos" probably refers to Azatoth, it likely refers to atleast Class 6, possibly Class X.
 * You greatly underestimate the ensuing destruction. All of existence is Azathoth's dream. When he wakes up, it will be over. No Earthshattering Kaboom, all reality will just be gone.
 * Second Earth in Earth 2350 has this happen to it at the hands of genocidal aliens.
 * Dragonlance has one of its characters, Raistlin, try to become a god. After succeeding, he proceeds to dethrone others to get rid of competition, however after he's done kicking all the other gods out of their seats the world is pretty much dead.
 * Frank Herbert's Dune series, as well as the sequels by Brian Herbert and Kevin Anderson include the Obliterator weapon. This weapon was stolen from the Machine Empire by the Honored Matres and used in a Scorched Earth retreat across the galaxy. They later use an Obliterator against Arrakis in an attempt to destroy the natural source of spice and a number of their enemies (including Darwi Odrade, Sheanna, and Duncan Idaho). In the Dune sequels, the Guild Navigators use an Obliterator against Richesse at the behest of the Honored Matre rebels to cripple the Bene Gesserit. Although the use of the Obliterator destroys all life on the planet, it's later revealed that a number of the worms of Dune knew that the attack would come (being possessed with prescience thanks to Leto II) and survived the attack by burrowing deep into the planet's crust.
 * In the Wing Commander novel Fleet Action, the Kilrathi on the warpath use Strontium-90 clad thermonuclear weapons to render several planets incapable of sustaining any life, and threaten to do so to Earth until Max Krueger's Big Damn Heroes moment.
 * If the F'dor of the Symphony of Ages succeed, the entire world will be reduced to lifeless, molten slag. This isn't just supposition by characters, either; Meridion's story bits take place After the End.

Live-Action TV

 * The Slitheen family from Doctor Who wish to enact this on Earth to make a profit. By inciting a world-wide nuclear armageddon, they would be able to sell off the radioactive "molten slag" left over as cheap fuel.
 * Two years later, in The Sarah Jane Adventures, more members of the Slitheen family nearly put out the Earth's sun, so they can scavenge the dead planet to the highest bidder. The Veil Androvax's homeworld is also left uninhabitable by the sun going out.
 * Planet of the Dead has a Horde of Alien Locusts that devour every living thing on a planet, turning it into a desert, before creating a portal to the next world. Before the Doctor interfered, Earth was next on the menu.
 * The planned bombardment of the Founder homeworld in the Star Trek: Deep Space Nine episode "The Die Is Cast"  apparently would have involved destroying the planet's crust and mantle. Well, at least the core would have still been there.
 * In Star Trek: Voyager, there was a weapon that could eliminate a civilization from history. Any planet that would have been terraformed by said civilizations in the original timeline would not have been terraformed (at least by the civilizations that terraformed them) so they would no longer have ever had life on them.
 * This is what essentially happened to Mal's homeworld of Shadow during the Unification War in the backstory of Firefly.
 * And Earth itself, really the catalyst for the entire series universe, albeit via pollution, and over a very, very long time.
 * In Babylon 5, although the is less thorough than its  counterpart, it's still pretty damn nasty. Enveloping the entire target planet in a Nanotech "death cloud" that fires thousands of multi-gigaton missiles deep into the planet's crust. The resulting detonations turn the entire crust over, blast away the atmosphere, and leave the planet looking more like Mercury than the habitable world it once was.

Music

 * In Food for the Gods, all life on Earth is destroyed by an unnamed super-weapon. Then it gets worse.

Tabletop Games

 * The "Crucible Of God" scenario in Vampire: The Masquerade's final supplement ends in this if the PCs lose; thanks to the war between humanity, vampires, and the Antediluvians, all life has been scoured from the face of earth, leaving it completely barren and devoid of even the most basic forms of life. Appropriately, the only survivors are the unliving vampire player characters, who either drain each other dry in a futile attempt to survive, lapse into a torpor that will never end, or kill themselves via sunlight.
 * Yet another Warhammer 40,000 example: this usually happens to planets when Chaos, Tyraniods or Necrons win. Not even unicellular organisms can escape their nightmarish campaigns.
 * Or if they lose, and someone calls on some of the less extreme forms of Exterminatus. (With the more severe ones, there isn't a planet left afterwards.)
 * Special mention to the Iron Warriors short story "The Heraclitus Effect", in which Honsou uses an experimental agricultural aid to hyper-accelerate the growth of remnant Tyranid growths on - out of spite.
 * In the Dungeons & Dragons Splat book Elder Evils, this is the most likely worst case scenario for Atropus, the World Born Dead. Should the players lose, his evil necromantic influence would turn the game world into a lifeless husk overrun with the undead.

Videogames
"Murozond: I have witnessed the true End Time. THIS? This is a blessing you simply cannot comprehend!"
 * The world of Armored Core 4 is gradually being poisoned by the massive amounts of radiation being released into the planet's atmosphere beceause of the wanton overuse of Kojima weapons, which are weapons that utilize Kojima particles, a newly discovered particle which allows for a practically limitless source of energy, at the cost of tremendous ecological impact.
 * By the time the sequel, Armored Core 4 Answer, finally rolls around, most of the world is already barren desert, entire regions have been abandoned because of Kojima contamination and over half of humanity now lives in Cradles, huge flying cities cruising at an elevation where the atmosphere is still safe enough to breathe, at least for now.
 * The Corporations even know full well that the Cradle System is just a stop gap measure, and that the entire atmosphere will eventually succumb to irradiation. But even before that, the Cradles will eventually be pushed to a high enough elevation that the automatic Kill Sats they placed earlier will eventually detect the cities as a threat and fire at them with their cannons.
 * Persona 2:
 * Halo - the book "The Fall of Reach" states that when the Covenant are fighting a losing battle on a planet, they will retreat to space and "Glass" the world. A systematic bombardment of the planet's surface with plasma weaponry vaporizes the ecosphere and reduces the surface to a uniform glassy mineral. They do that even if they win, being Omnicidal Maniacs.
 * Later sources rectify this: the Covenant don't actually have the ability to glass an entire planet and wage a large-scale war at the same time. The damage is still catastrophic, but many planets with minimal importance to the war effort aren't concentrated as much upon, and some people have even survived the glassing and survived for years afterwards. And restoration of the planets are possible.
 * The UNSC have the NOVA Bomb, which blows up planets.
 * Happens to Vasuda Prime in Free Space, due to orbital bombardment with Shivan beams. The Vasudan species survived due to a number of colonized systems and a massive evacuation of the planet beforehand (though around 4 billion still died during the bombardment). Also happened to the Ancients' home system in the backstory, and the game ends with the player's squadron just barely stopping the same thing from happening to Earth.
 * Tiberium does this rather slowly, but extremely effectively. As of the third game, 30% of the Earth's surface is already at this level, 50% is getting there and the remaining 20% is being held at bay with sonic technology that requires so much energy that tiberium is the only thing that can power it.
 * It actually almost happened twice. At the beginning of the GDI campaign of Firestorm, a scientist mentions that if they won't do anything, Tiberium biosynthesis will make the planet inhospitable to carbon-based life in less than a year. Fortunately for everyone, GDI got their hands on the Tacitus and figured out the effect of sonic weapons on Tiberium. Then after the third game, the planet was once again heading towards this... until Kane decided to give the Tacitus' copy to GDI and helped them build the Tiberium Control Network.
 * The Scrin's modus operandi is somewhat similar to the Tyranids from Warhammer 40k: drop Tiberium onto an inhabited planet, wait a few decades until the whole surface is consumed including native life then swoop down and harvest, leaving a barren rock behind.
 * In Adventure Quest Worlds, this was the ultimate plan of Chaos Lord Ledgermayne, the Big Bad of the Arcangrove saga, by cutting off the Para-Elemental Plane of Magic from Lore. Since magic is tied to life itself, this would have resulted in the end of all life in the world of Lore. Ledgermayne was stopped by The Hero before he could bring this plan to pass.
 * In RuneScape, Goblins used to live peacefully on a colorful swamp world called Yu'biusk. Then the war god, Bandos, found it. After thousands of years under Bandos' rule, the ground is black and scorched, the sky is smoky and dark, and the water looks like it could kill you just by you touching it. The entire world has been deserted, desolate, and ravaged. It's a bit depressing.
 * This is the goal of the Old Gods in World of Warcraft, bar themselves and their minions (although they arguably don't count as alive anyway, being said to be "outside the cycle"). The dungeon End Time takes players to a Bad Future where this has happened, where the Old Gods' Dragon (pardon the pun) Deathwing has even killed himself. It's implied that this is the best possible end of the world for Azeroth!

Webcomics

 * At the conclusion of the Revenge of the Sith arc in Darths and Droids it was discovered that.
 * Spacetrawler. When a group of Eebs is liberated from slavery, they decide to demonstrate how pissed off they are by raining telepathic fire upon planet Carpsellon and melting its surface to slag.

Web Originals

 * In The Gungan Council, a rogue moon crashes into Taris in "The Galactic Crusade". Everything dies.

Western Animation

 * Played for Laughs and exaggerated in SpongeBob SquarePants when Patrick tells the story of The Ugly Barnacle, "He was so ugly that everyone died. The end." Though Patrick could have easily been an Unreliable Narrator when telling the story, or telling a fictional story.

Real Life

 * Scientists predict that the Sun's luminosity gradually increases; in about a billion years, Earth will become too hot to sustain life.
 * Possible example of what the future may hold for Earth: our nearest neighbour, Venus.
 * Venus is hotter than it should be though, due to the cloud cover. Scientists have actually hypothesized that if they could blow off enough of the atmosphere, the poles would be able to sustain human life.
 * And could be worse than Venus. In about 3.5-4 billion years, Sun's increasing luminosity may induce a greenhouse effect so powerful that Earth's surface temperature may rise enough to melt rocks. And this still a few billion years before the Sun becomes a red giant.
 * Perhaps there's some hope for life; while Earth's surface may be too hot to sustain life, there's a lot of water in the deep crust and mantle that could maintain it (albeit at a very simple level; ie bacteria and very little, if any, more complex) there. Also, the future Venus-like Earth and the hellish Earth depicted above respectively depends of the level of tectonic activity and the amount of water in Earth's atmosphere. If tectonic activity is low enough (or stops) and there's little water remaining these two scenarios could be avoided, so life could still be around until the Sun started its path to become a red giant.