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 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.

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.

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.
 * 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 one in Sword of the Stars 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.

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. Beta Hydri is only 7.46 parsecs away.