Apocalypse How/Class X-5

Multiversal-scale Physical Annihilation. If there are alternate dimensions or different realities or whatever in this fiction, then many of those go away.

Anime and Manga

 * Bokurano: If you lose the game, your universe goes bye-bye.
 * The standard effects of a Lost Logia reaching full power and going out of control in Magical Girl Lyrical Nanoha are multi-dimensional catastrophes that destroy many worlds in the process.
 * In Noein, the goal of the title Big Bad is to destroy all possible parallel universes so that only Shangri'La remains.
 * Attempted by Apocalymon in Digimon Adventure
 * Bagramon's goal in Digimon Xros Wars. He doesn't succeed.
 * This is the goal for the Shadow Dragons in Dragon Ball GT

Comicbooks

 * Crisis On Infinite Earths destroyed almost the entire multiverse and squished the surviving few universes into a messy amalgam universe. Prior to this, the Anti-Monitor destroyed, ultimately, infinity minus five universes.
 * In JLA-Avengers there was Krona, a being that attempted the destruction of the core universes of both DC and Marvel, in order to remake the new universe that would emerge in his own image.
 * In the Marvel Comics, Unicron from Transformers has this as part of his background. He ate most of the previous universe and went to sleep, only to have the scraps he left behind form a new universe while he slept. Now he wants to make sure it doesn't happen again.

Literature

 * City At The End Of Time, by Greg Bear, has the end of ALL universes come about (semi?-)naturally, around about the year 100 trillion, at the hands of the strange, physics-warping Typhon. Even better, the destruction travels backwards in time and screws around with modern-day Seattle..
 * In Riddle of the Seven Realms by Lyndon Hardy,
 * The Dark Tower -- this is what happens if the Tower falls - the utter chaotic destruction of every single universe, dimension, plane, time, space etc etc. The Big Bad want to this because he claims he will be able to rule the chaos that will exist forever afterwards; whether or not this is true is debatable, but the fact that he expects something to be left makes it this and not Class Z. The worrying part is that this is starting to happen already at the beginning of the series. Even more scary is that protagonist has to succeed every single time. The antagonist just has to win once.

Live-Action TV

 * In the 2010 finale of Doctor Who, after, all that remains of every reality is that of Earth in this universe, just a stone's throw from Class Z. Stars are myths , all that's left of the Daleks is one shadow in time, and as the characters edge closer to the date of , people start vanishing from time. This is reset by.
 * 'Remains' is debatable, given everything

Videogames

 * The first Kingdom Hearts game has this, although it's not discussed often (likely due to the younger target audience). When the story starts, a seemingly endless hoard of planet-devouering hellspawn is already well underway at tearing the multiverse apart at the seams. Traverse Town, a sort of base-camp for your character, is literally an interdimensional refugee camp for people who managed to survive their world's utter annihilation.
 * The Time Devourer attempts to consume all of space-time as revenge for being banished to the Darkness Beyond Time.
 * At the end of VVVVVV, you have to destabilize the dimension to get back to your own. However, this has destabilized two dimensions so after the ending you have to find a way to fix them.
 * In Bayonetta, Balder wants to instigate this in order to reunite the Trinity of Realities, which in turn, would destroy all life in the current universe to do so.
 * Featured in the Bad Ending of Demon Path (when you win the final battle, that is) in Soul Nomad. Just because it was fun.

Webcomics

 * In Homestuck, this would be the eventual result of Lord English's passage through the multiverse: he destroys universes one by one. So far he is outspeeded by creation of new universes, though.


 * In Melonpool, an excess of Time Travel going horribly wrong results in this.

Western Animation

 * At the end of Spider-Man the Animated Series, a Carnage-Spiderman (called "Spider-Carnage" in-show) attempts to destroy the multiverse, aching to a Class Z destruction (although it probably wouldn't count that far, since those sent to stop him are alternate Spidermen, which probably means only the Universes containing or related to Spiderman would be destroyed).
 * Similarly, in Turtles Forever Utrom Shredder destroys his native dimension and begins destroying another, eventually wiping out every universe that contains the Teenage Mutant Ninja Turtles.
 * Nearly happens twice in Danny Phantom; First when the Guys in White try to destroy the Ghost zone, and again in the finale when Earth is threatened by the "Disasteroid" These apocalypses would have been possible because the Ghost Zone and Earth are opposite dimensions and the destruction of one will destroy the other.

Real Life

 * In a way, the heat death of the universe. If the many-world interpetation is the correct view of reality, then universes who split off from our own are similarly going to suffer heat death. And, since such event is inevitable, they will all die out at about the same time.
 * That sounds questionable, since the increase of entropy is only inevitable due to probability. If the many-world interpretation were true, then the possible futures might also include completely unlikely events, such as a spontaneous local decrease in entropy or the Earth suddenly turning into banana pudding.