Trope Workshop:Planet Killer

Because Earth-Shattering Kabooms don't cause themselves. (Usually.)

The Planet Killer is Exactly What It Says on the Tin: a killer of planets. It might be a Doomsday Device (a sufficiently-powerful Wave Motion Gun might be able to do it), or a magic spell, or a Person of Mass Destruction, or a natural phenomenon — it doesn't matter. What matters is the result, and Apocalypse How calls the result "Planetary/Physical Annihilation".

Compare with Planet Eater, which is something or someone that uses planets for nourishment but might leave the planet itself intact; and Earth-Shattering Kaboom, which is one possible result of a Planet Killer's activation.

Note: The Other Tropes Wiki redirected "Planet Killer" to "Earth-Shattering Kaboom", confusing a cause with an effect.

Anime and Manga

 * From Sailor Moon, there's Sailor Saturn, who can destroy an entire world with a swing of the Silence Glaive.
 * In the Junji Ito miniseries Remina, the titular entity enters galaxies to eat planets. Earth happens to be next on its menu.

Fan Works

 * Several varieties show up in the Ranma ½/Sailor Moon crossover Heir to the Empire by Ozzallos:
 * The xenophobic civilization The Emblem glassed two planets that were part of the Silver Millennium civilization with nuclear saturation bombing. While the planets themselves were not physically destroyed, they were rendered completely dead, sterile hunks of radioactive rock.  A piece of slag from one of these planets, Meridian, was slowly transformed into the Ginzuishou by Queen Serenity as a tribute to the lost people of that world and as a symbol of her intention to restore its ecosphere somehow, some day.
 * Queen Serenity retaliates for the destruction of Meridian and Cambriea by bringing a fleet to The Emblem's capitol planet/home world and launching six Z90 Point Singularity torpedoes at it -- when four would have been sufficient to destroy it. The planet is torn apart by and vanishes into the eager maws of six miniature black holes.
 * The Z90s, which are tactical fleet-based weapons, were not the only planet killers in the Silver Millennium arsenal. In a different flashback, as a distraught Serenity threatens to destroy multiple planets in retaliation for the murder of her consort, we learn they had several such weapons, described as "a cocktail of total annihilation", including the XA-505 "Nova Bomb", designed for system-to-system bombardment.
 * In yet another flashback, we learn that Sailor Saturn vaporized a planet called Phaelon during Beryl's assault on the Silver Millennium.
 * At the climax of the story, triggers its Self-Destruct Mechanism, which is designed to take not only itself out but the entire Earth with it.
 * Less two months after they've been "partnered" in the Worm/Luna Varga fic Taylor Varga, Taylor Hebert and The Varga have come up with at least a dozen ways their combined power and knowledge can be used to destroy a, or the, world -- including a couple that do so as a side effect of an even greater destruction.
 * In a non-canonical omake, the Family makes a web series about different forms of planetary destruction, which they call WorldBusters.

Film

 * The Drej use one to destroy Earth in Titan A.E..
 * The deleted "Dream Scene" in The Iron Giant shows that the giant was intended to be one.
 * Both Death Stars from Star Wars. Although quite effective, they were relatively short-distance weapons which needed to be practically on top of their targets to hit them.  The First Order's Starkiller (first seen in The Force Awakens) was a dramatic improvement over the Death Star, sending its deadly beam through hyperspace to attack planets in a completely different star system from the one in which it was based.
 * The Destructo-Vision employed by Darph Nader to destroy the peaceful planet Basketball in Hardware Wars.
 * The Genesis Device from Star Trek II: The Wrath of Khan, as pointed out by Dr. McCoy, could destroy a planet and replace it with a different planet. Assuming it worked properly, which the next movie showed was a bad assumption.

Literature

 * John Stith's novel Manhattan Transfer begins with aliens tossing a dome over and ripping out Manhattan Island without any obvious explanation, then stowing it inside their massive spacecraft... to save a sample of humanity from a soon-to-arrive Planet Killer.
 * Second Stage Lensmen, as part of the prototypical Lensman Arms Race, has the "nutcracker": two planets that are remotely piloted so that they both hit a third planet at the same time. This crushes the third planet between them.

Live-Action TV

 * The titular "Doomsday Machine" in the Star Trek: The Original Series episode of the same name. It takes the destruction of a starship to render it inert.
 * The Shadows in Babylon 5 have at least one; Captain Anderson takes it out.
 * The Vorlons have a swarm-based system that bombards a planet with an immense number of (relatively) small projectiles.
 * In Lexx, Lexx itself is a Planet Killer.

Video Games

 * The Alpha Strike in Iji.
 * Wild ARMs 2 has an entire living universe that eats worlds.
 * In Wing Commander III, the humans had two planet killers, one of which is called Behemoth. The more reliable one was taken out by the Kilrathi.
 * The System Killer in Sword of the Stars is one of the Grand Menaces. It spawns at one end of the galaxy, draws a line to a point on the other side, and tries to visit all star systems within 6 lightyears of that line. If not destroyed before it initiates combat in a star system, the system will be destroyed, star, planets and all. To make matters worse, it somehow repairs all damage as a result of this. Fortunately, it can be intercepted in interstellar space and worn down over multiple encounters. It has the Fan Nickname "Sparky".
 * The Ultima Spell, cast by in Final Fantasy IX, combines Planet Killer, Nuke'Em, and Rocks Fall, Everyone Dies.

Web Comics

 * Every single Drive-equipped ship in the web comic Drive can cause seismic events on a planet by pinching too close to it. In Real Life, a magnitude 14 earthquake would be sufficient to tear a planet apart, and a ship that is big enough in-universe can invoke that powerful an event.
 * The original Exterminatus in Exterminatus Now.

Western Animation

 * Screwing the Illudium Q-36 Explosive Space Modulator into its eyepiece turns Marvin the Martian's telescope into one of these in the Looney Tunes short Hare-Way to the Stars. Fortunately, Bugs Bunny snuffs the fuse and makes off with it before it can go off.
 * The Planet-Jackers from Invader Zim use a specially-designed spacecraft to capture planets and then drop them into their sun.
 * Wander Over Yonder features Lord Dominator in Season Two, whose ship is able to drain planets using an internal excavator engine..

Real Life

 * The supernova of a sufficiently close subgiant star would be enough to scour all life from the side of the Earth that faced the shockwave, downplaying this trope. Beta Hydri is only 7.46 parsecs away.