So you've got a star. Main sequence type, more or less middle of its life-cycle, nothing special. Probably has an inhabited planet or two orbiting it. Of course, the Evil (Space!) Empire wants the people on the planet(s) dead. They could just carpet bomb the planet or maybe even blow it up, but instead they decide to go for broke. When a faction or character goes Star-Killing they go about ending a star's life in any of a variety of ways that dooms all life in the system to a Class X-2 Apocalypse How.
On the "soft" end of the scale, the sun may have the equivalent of food coloring added, changing the visible spectrum (and radiation) it emits, killing or weakening all life and/or sentients. This is the equivalent of changing Earth's sun from power granting yellow to kryptonite green for Superman.
Next up is poisoning the sun such that it ages several billion years, depleting its hydrogen content and making it a cold dwarf star; or making it impossible for it to conduct hydrogen fusion, resulting in an atypical supernova. Of course, the bad guys might somehow apply enough firepower to literally blow up the sun (or cause it to go nova). Lastly, they might somehow collapse it into a singularity (again, atypical for the mass of many suns) or simply shoot the singularity into the star and have it get eaten from the inside out.
Interestingly, whatever means are used to kill the star might not harm any other stellar body it's aimed at. This is especially true for the "fusion-stopping" type poisons. If this poisoning takes long enough, the heroes may be able to apply an Magic Antidote, administer life-saving Solar CPR, or use an extremely powerful World-Healing Wave on the star. See also Black Holes Suck.
- In Green Lantern, the Sun-Eater was killing Earth's sun, Hal Jordan does a Heroic Sacrifice that saves it and restores the damage. In the process, it shone green for a day.
- In All-Star Superman: Solaris the Tyrant Sun turns the sun red in order to strip Superman of his powers. Later, the sun turns blue and it's revealed that Solaris poisoned the sun. Superman seemingly sacrifices himself in order to fix the sun.
- An early issue of Marvel's Epic Illustrated includes a story about an attempt to tap energy directly from the core of the Earth's sun. This goes horribly wrong, causing the sun to go nova.
- Star Trek Generations revolves around stopping the use of a missile capable of stopping all fusion in a star, causing a near instant nova.
- The "Star Harvester" from Transformers: Revenge of the Fallen. The Fallen wants to use it so he can destroy the entire Solar System.
- The original name for the Skywalkers in early drafts of Star Wars was "Starkiller". This has popped up a few times in the expanded universe.
- Larry Niven short story "The Fourth Profession". The Monks are a species of alien traders who travel from star to star. Normally they travel using light sails pushed by launching lasers built by intelligent races in the systems they visit. If there's no intelligent race in a system or the race refuses to build a launching laser for them, they use a device on their ship to make the system's star go nova and use that for propulsion.
- The SunCrusher from the Star Wars Expanded Universe.
- In For White Hill by Joe Haldeman hostile aliens make Earth's sun go nova. The plot is about making a memorial for Earth.
- Because Science Marches On, modern fanfiction for The Night Land generally treats the death of the sun in the Backstory as artificial instead of natural.
- In the Galactic Center series by Gregory Benford it is implied that the mechs are the cause behind a number of recent novas.
- In the Revelation Space books, the Inhibitors "sing" Delta Pavonis apart in order to destroy the local human colony: having already wiped out one species native to the system millennia ago, they're determined to do the job for good this time. It's also offhandedly mentioned that they know of fifteen different ways to destroy a dwarf star.
- Not only do they kill the star, but they turn it into a huge Flamethrower
- A novel by Barrington J. Bayley included a weapon which worked by eliminating all of the electrons in a star, thereby rendering fusion impossible. A star hit by the weapon would lose 1/1400 of its mass and instantly go out.
- The Star Trek Expanded Universe novel trilogy The Q Continuum suggests the supernova that destroyed the homeworld of the Tkon Empire (as seen in the TNG episode "The Last Outpost") was caused by an omnipotent being that Q unleashed. This would answer the question of why a technologically advanced civilization with the power to move entire star systems could have been taken by surprise by a supernova.
- The Ascendants in the Star Trek Deep Space Nine Relaunch have a weapon capable of destroying stars, as seen in Worlds of Deep Space Nine: The Dominion.
- An appendix to Iain M. Banks' Consider Phlebas summarises the vast interstellar war the novel was set in, with a casual mention that among the tally of destruction was six stars. In a later book, we learn that one of them harboured an inhabited planet.
- The titular "iron-bombing" of Moscow's star in Iron Sunrise by Charles Stross. Not an "iron bomb" in the USAF sense of the word, the process involves sending the target star's core into a Pocket Dimension with a vastly accelerated time flow. As quintillions of years pass in the mini-universe, the superheated hydrogen cools and eventually transmutes through quantum tunneling into a solid iron crystal. When the now-shrunken core is returned to the center of the star, the outer layers fall toward it, bounce off (iron doesn't like to be fused) and rebound explosively. The entire process is a fair approximation of what actually occurs in a Type II supernova (apart from the pocket dimension, anyway).
- In the final Lensman novel of E. E. "Doc" Smith, "Children of the Lens", the sun of the Ploor system is destroyed by firing a planet from another universe whose intrinsic velocity is always faster than light into the star.
- The Lone Power of the Young Wizards series can both cause a star to suddenly stop radiating light (by presumably supernatural means), and also cause a star to go nova (by presumably more scientific means). This gives It one of Its many names, "Star Snuffer".
- Life, the Universe, and Everything has at the heart of the plot a bomb that would cause every sun in the universe to go supernova at once, resulting in complete annihilation.
- In Down The Bright Way by Robert Reed, the UnFound are wiped out on each separate Earth via star killing. Since the UnFound inhabit every planet, and thousands upon thousands of asteroids and comets in each Earth's solar system, making the sun burn away most of its mass in a miniature supernova becomes the most effective way to kill the UnFound.
- The aliens that live inside stars described in Frederik Pohl's novel The World at the End of Time have the nasty habit of attacking each other causing the stars where they live to go nova without any regards to the people that could live in the planets orbiting them, as occurred with the humans on Earth. However, it does not totally qualify since the affected stars "heal" after some millennia.
- In Babylon 5 it's implied that the far future dying of our sun is caused by humanity's enemies.
- Babylon 5 actually used this trope twice. During the Dilgar War, the Earth Alliance helped the League of Nonaligned Worlds to beat back the Dilgar forces until they had all retreated to their home system. Then the sun went nova. Word of God says that there was no natural reason for their sun to do that when it did.
- There is the Hand Of Omega, from classic Doctor Who which is a remote stellar manipulator the Time Lords use to tinker with stars to make them do as they wish, in "Remembrance Of The Daleks" the Doctor uses it to destroy the Skaro solar system. In New Who the Doctor uses the energy of a supernova to talk to Rose the first time she got dumped into another dimension, although he doesn't actually say he caused it.
- Stargate SG-1. "Remember that time when you blew up a sun?" An oft-referred-to incident where the team basically just dropped an open Stargate (connected to some far-off world orbiting a Black Hole) into a star, causing a fatal instability and immediate supernova, in order to wipe out an incoming armada.
- SG-1 also once poisoned a sun accidentally when a wormhole's trajectory passed through it and dropped superheavy elements as it passed. They (or the Asgard; they never actually clear that up) manage to fix it by the end of the episode.
- In the TV Series Andromeda, Commonwealth warships had a complement of 40 NovaBombs - missiles designed to destroy a star by cancelling out any gravitational forces, literally, pulling it apart and causing it to explode. In the pilot the Andromeda Ascendant uses up her entire complement canceling out a black hole's gravity.
- In Star Trek: Deep Space Nine, a Changeling infiltrator posing as Bashir had planned on dropping a protomatter weapon into Bajor's star to wipe out a combined Klingon/Federation/Romulan taskforce (how useful that would have been in doing that is questionable, since the ships could easily go to warp, but it would wipe out Deep Space Nine and Bajor, and allow the Dominion to come out after the wake of the supernova and secure the Alpha Quadrant side of the wormhole)
- Traveller. The Darrian race has the Star Trigger: a device that can cause a star to give off solar flares which devastate planets and destroy all electronic devices. The flares are powerful enough to affect planets in nearby solar systems. It was discovered by accident, nearly destroying one of their home systems; they have since re-created it to use as a deterrent weapon of mass destruction. Actually, they haven't - this is just a bluff.
- StarForce Alpha Centauri. The Xenophobe race can cause stars to go nova, incinerating the planets in the system.
- Star Fleet Battles. In one scenario a Sun Snake will approach and try to dive into a star. If it succeeds, the star will go nova.
- The C'tan star gods in Warhammer 40,000 are Energy Beings that feed off elecromagnetic radiation released by stars. This apparently makes the star unstable, as it's implied that the deadly radition given off by the star of the Necrontyr homeworld was because of the C'tan living on it. However, if the star is eventually destroyed by the process, it takes a very long time (the Necrontyr lived with their deadly star for millenia), so it doesn't necessarily fully fit this trope.
- The indie 4X game, Star Ruler allows you to blow up stars (and anything else). It's possible to destroy a star using tens of thousands of tiny ships, or one ship that's comparable in size to the star itself. Destroying a star causes it to go supernova and quickly kill anything in the system, which usually includes your star-killer unless your shielding, armour and ship construction techs are high enough. Around a trillion health will do the trick.
- Galactic Civilizations II allows you to build a (painfully slow) ship that can detonate a star, and turn all planets around t into asteroid fields. Of course, it's a great example of Awesome but Impractical
- In Mass Effect 2, recruiting Tali has her investigating a sun which is dying too quickly to be natural and giving off harmful radiation. Her loyalty mission confirms that dark energy is reducing the mass of the star's interior, and no-one knows who or what is responsible. It screams foreshadowing, but became an Aborted Arc - nothing came of it in the third game.
- At the end of Super Mario Galaxy, Bowser's sun, or his molten planet next to his sun (it is presented strangely), actually explodes shortly after he is defeated by Mario. The sun then causes the universe to implode, until it is recreated by the Lumas jumping into the black hole and sacrificing themselves.
- One level of Super Mario Bros 3 actually involved killing the Sun with a Koopa shell!
- In RPG Shooter Starwish, Bamboo's sun was turned into a black hole by accident before the game. It happens again during the game, but the star killer just wants the star, and surrenders her power so the orbiting planet and its inhabitants may be saved.
- The Shivans of Free Space wind up destroying the Capella system in a massive supernova at the end of the second game. Well over a decade after the games' release and the franchise's abandonment, there are still no clear answers as to why or how they accomplished this.
- In the Space Empires series, blowing up a star destroys everything in the system. If that's not enough, you can turn it into a black hole, which also destroys the raw materials you can use to recreate planets.
- In Quentyn Quinn, Space Ranger the Empire of the Seven Systems (the good guys FYI) used a stellar lance on the Kvrk-chk as a deterrent.
- Homestuck: Destroying the Green Sun, a star twice the size of Earth's universe and the source of the powers of First Guardians (and by extension Jack Noir), was one of the three means by which the kids intend to deal with how fucked up their Sburb session is; Rose Lalonde and Dave Strider travelled to the Sun with a bomb of sufficient power to destroy it with the intent of doing so. Subverted in spectacular fashion with the reveal that they were tricked into literally creating the Sun.
- In Schlock Mercenary, the Pa'anuri tend to react to the use of gravitics (which are painful to them) by snuffing out the stars of inhabited worlds where the use occurs. If prevented from doing so, they'll find a nearby undefended star and make it go supernova.