The Purge

When a character, usually a villain, takes over The Government, The Syndicate, the Ancient Conspiracy, or otherwise takes power in some way, often the first item on the character's agenda is ordering the deaths of many characters. These aren't just Muggles, though; these are characters we know (and possibly love) from before, killed off in a quick montage in various locales. No big ceremony, just them dying horribly. Hits home just how powerful the guy is.

The people the character does kill with ceremony don't count.

If this is in a character's Backstory, usually leads to Last of His Kind.

Examples of The Purge include:

Anime and Manga

The Uchiha Massacre in Naruto, which is the driving force behind the second main character of the story. We later find out that the one who committed the purge was acting on orders from the village council and well-intentioned extremist Danzo to do so, and that the Uchiha clan had been planning a coup.
After his Memory Gambit is over, Light does this in Death Note, killing off a lot of people.
Hellsing has one with the Vampire Nazis taking over.
- It doesn't help that Enrico (who was just named an archbishop) was doing his own purge on Protestants at the same time.
Third Impact from Neon Genesis Evangelion. Also implied in the original Gainax Ending when several characters are seen after apparently being shot.
The most recent arc boss from One Piece recently killed all his lovable Quirky Miniboss Squad zombies so he could eat their shadows (don't ask) and gain more power.
In Cowboy Bebop, the Red Dragon, after Vicious attempts to take over the syndicate, orders the deaths of everyone connected to him, including the crew of the Bebop, in episode 25. The crew of the Bebop escape death, along with Spike's long lost love Julia, and Vicious succeeds in his second attempt to take power, setting up Episode 26's final showdown.
In Claymore, The Northern Campaign was essentially a purge of the more rebellious Claymores. The Seven who survived are, as of the present storyline, hiding to conceal the fact that they survived.
Happens quite a few time in Gundam:
- Char & Sayla from the classic Mobile Suit Gundam spent most of their childhoods avoiding a purge of their father's supporters after his untimely death due to heart problems/complications of heart surgery/poisoning & the subsequent rise of the sinister Zabi dynasty.
- In Zeta Gundam the Titans conduct a larger scale purge of their rivals in The Federation & the colonies.
- In Gundam Wing we get to see one of these after OZ overthrows the Alliance, culminating with their leader being kicked out the back of a cargo jet AND shot in head on his way down for good measure.
- In Gundam AGE, the second generation ends with a Purge is undertaken by the main character, taking out any government officials who were collaborating with Vagan.
Happens in the climax of Eureka Seven.
The action in Romeo X Juliet starts 14 years after the purge of the Capulet clan.

Comic Books

"The Days of Future Past" storyline in X-Men had various team members having been hunted down and killed.

Film

Palpatine's Order 66 from Star Wars: Revenge of the Sith, which shows Jedi all over the galaxy being ruthlessly murdered by the clone troopers. Though we don't see much of it, there's also Anakin's leading the 501st legion into the Jedi Temple.
- There's also the massacre of the Separatist leaders by Anakin, while Palpatine has a speech that reforms The Republic into The Empire.
The Godfather has the famous baptism scene, where Michael takes power by wiping out the other Dons (and Moe Green) during a baptism. This and the above Star Wars examples are particularly well-known.
- This was later parodied in a similar scene in the spoof movie Mafia! that featured death by fart (no, really).
Goodfellas has Jimmy authorizing the murders of everyone involved in a botched heist.
In the movie Elizabeth, Sir Francis Walshingham's agents do the killing part.
Infernal Affairs II has the killing of the four Ngai family capos half-way through.
In Lethal Weapon 2, the villain, a South African drug smuggler and diplomat orders the deaths of the LAPD detectives investigating his illegal operations. Most of them are brutally killed in their homes with Riggs and Murtaugh the only survivors.
Judge Dredd. Rico and Ilsa manage to massacre more than a hundred street Judges due to Griffin's knowledge of Judge procedures, security measures and scrambled radio frequencies.
G.I. Joe: Retaliation has Zartan-disguised-as-President ordering the destruction of the Joe base.
This is what happened to the ISO's prior the events of Tron: Legacy. Bonus points for actually being called The Purge in story.

Literature

Older Than Feudalism: There are several examples in The Bible: The Flood is a form of Purge, Pharaoh attempted to have the Israelite newborns killed, one of the Ten Plagues of Egypt is The Purge of all the firstborn sons in the country, Solomon began his reign by having a number of people previously spared by David executed/assassinated, Jezebel and Ahab slaughtered dozens of prophets...and this is just a sampling.
In the also biblical story of Esther, Haman plots to have all the Jews executed. Esther manages to save them in the end.
In The Diamond Chariot, when Erast Fandorin comes too close to uncovering the villain's identity, the villain sends four ninjas to assassinate him and his investigative team simultaneously. He is the only one to survive because the ninja princess has fallen in love with him and demands him to be spared.
Animal Farm had one based on Stalin's Great Purge.
Death Eaters takes over Ministry in Harry Potter.
Kangaroo courts a-plenty, mass round-ups in the night followed by executions on the same scale, and probably several assassinations just for variety kicked off the takeover of the People's Republic of Haven, in the Honorverse.
Torak pulled this in the Belgariad prequels. He'd been living in isolation for centuries, so when he was ready to lead an Angarak army against the West his first step was "remind everyone who's in charge here".
In the Star Trek novel series Terok Nor, Cardassian Central Command destroys the Oralian Way religion (although pockets manage to survive) in a purge of believers in the enclaves on Bajor. The Oralians had already fled persecution on Cardassia, but of course Central Command had its eyes on Bajor, too.
Inverted in The Wheel of Time: after securing her position on the Amyrlin Seat, Egwene attempts a purge on the Black Ajah, which results in more than fifty executions, although word gets out before she can attempt to capture the majority of them.

Live-Action TV

Lost: the "Hostiles" execute most members of the Dharma Initiative using poison gas.
In the first season of Lexx His Shadow eventually orders the deaths of everybody in the Cluster, and plans to do the same for the entire human race unless our (anti)heroes can stop him.
Children of Dune, the Sci-Fi miniseries adaptation of the second and third Dune books, staged Paul's elimination of the conspirators against him much like the famous Godfather scene above. The book wasn't quite as theatrical.
The season one finale of Boardwalk Empire has a quick elimination of the D'alessio brothers.
The first episode of Game of Thrones season two ends with the City Watch killing most of the late King Robert's bastard children.
On I, Claudius Upon learning of his plot to seize power, the Emperor Tiberius has Sejanus' family and supporters murdered.

Tabletop Games

Exalted has the Usurpation, wherein the Dragon-Blooded and the Sidereals conspired the overthrow the Solars (who'd gone a bit nuts by this point) and their Lunar mates. The Solars were wiped out pretty much down to the man, and their Exaltations gathered up and stuck in a mystical cage. The Lunars who weren't killed fled to the Wyld. The Dragon-Blooded set themselves up as rulers, and named the Solars and Lunars "Anathema" in their state religion. And the Sidereals wiped themselves from living memory, ruling from Heaven behind the scenes.
Vampire: The Masquerade had the Tremere pull this twice during the metaplot. During the Middle Ages, after Tremere diablerized Saulot to gain power on par with the other Antediluvians, he spread rumors that the Salubri were infernalists, and the other clans ended up purging them violently. In more recent history, the elders of the clan used a blood ritual to wipe out the Tremere Antitribu (every Tremere who'd broken from the Pyramid to join with the Sabbat).

Video Games

In the second mission from the undead campaign in Warcraft III: The Reign of Chaos, Arthas kills most of the Paladins, in order to obtain a magic item. The same fate is suffered by most of Dalaran's Archmagi when he have to retrieve another object. In The Frozen Throne, the remains of the Paladin Order reform, but Arthas shatters them again.
- Arthas is practically the embodiment of this trope; he purges the city of Stratholme to stop the citizens becoming undead, he purged the entire kingdom of Lordaeron after he became undead. "Purge" is probably one of his top ten words.
In Call of Duty: Modern Warfare 2, General Shepherd betrays Task Force 141 and personally executes Roach and Ghost. His men then start killing off the remaining members of the force. Price, Soap, and Nikolai are the only known survivors at the end of the game.
The Right of Annulment in Dragon Age is a special directive given by the Chantry to the Templars to initiate The Purge of all mages in Ferelden, starting with the very Circle of Magi. Depending on how you play the "Broken Circle" quest, the directive is given or called back. It's happened seventeen times in nine centuries over the course of the history of the Chantry.
- Regardless of your actions, the Right of Annulment is always invoked for an eighteen time, and many mages of the Kirkwall Circle die, in the end of Dragon Age II.
- Also, if Bhelen becomes King of Orzammar, he immediately orders the execution of his rival Lord Harrowmont. In Dragon Age II, it's revealed that his purged has extended to Harrowmont's relatives.
This happened in the backstory of Jade Empire: to steal the power of the Water Dragon, Emperor Sun Hai and his brothers launched a genocidal assault against the Spirit Monks of Dirge. The player character is revealed to be the last survivor of the attack.
In Final Fantasy XIII we have a purge called... The Purge. After discovering a Fal'Cie from Pulse in some ruins, the Sanctum government decides to send everyone that was "near" that Fal'Cie to Pulse because of the irrational fear of everything coming from that planet. Several facilities were constructed for the purged population to live happily there, and a military division known as PSICOM took over and oversaw the removal of the population. However, it quickly becomes apparent that the Sanctum government neither expected nor intended for any of the Purged population to survive - when the population being shipped out began to violently resist, PSICOM used that as an excuse to simply massacre everyone.
In Halo 2 the Prophets order the Brutes to do this to the Elites after the changing of the guard and subsequent schism within the Covenant.
A wood elf NPC in The Elder Scrolls V: Skyrim helps you to infiltrate the Thalmor embassy for the Blades during the main quest. Delphine notes he's doing this at least in part for revenge: his family was killed in "one of the Thalmor's purges you never hear about." When they took power the Thalmor also conducted a purge that killed every Blades agent in Valenwood and the Summerset Isles.

Web Original

In the Red Panda Adventures episode "There Will Be Rain Tonight", the entirety of the Home Team, along with Col. Fitzroy are assassinated when a spy leaks the identities of the heroes to the Nazis.

Western Animation

In Avatar: The Last Airbender, the destruction of the Air Nomads by Fire Lord Sozin qualifies, making Aang The Last Airbender.
- Not to mention Fire Lord Ozai's plan during the finale, which was to burn the entire Earth Kingdom to the ground. It was his daughter's idea, but the man ran with it and never looked back. However, no one really died (unless there were hermits in the Wulong Forest), as Aang, Toph, Suki, and Sokka put a stop to that.

Real Life

One of the earliest recorded purges in history (outside The Bible, of course) occurred after the end of the Peloponnesian War: the victorious Spartans, having installed an oligarchy of "Thirty Tyrants," leave Athens to its own devices. The Thirty proceed to first order the executions of all the democratic leaders; then all the potential democratic leaders; and finally all the suspected potential democratic leaders. Eventually, it got too much; the Athenians revolted, restored democracy, and gave a general amnesty. They then proceed to try and execute Socrates.
Pride's Purge during the English Civil War was, fittingly for an English event, Exactly What It Says on the Tin: In 1648, Colonel Thomas Pride forcibly removed all of the Members of Parliament he didn't like, opening the way for Oliver Cromwell to more or less become dictator. Atypically for a purge, but very typically for England, the "purged" MPs weren't actually killed, and then returned to Parliament after the Restoration of 1660.
The Night of the Long Knives was a Real Life purge of the SA leaders by the Nazis. This event was even named after an old Roman purge where Emperor Tiberius ordered the execution of Sejanus's family and supporters.
The Great Purges in Stalinist U.S.S.R.
The Khmer Rouge killed at least some 700,000 (and another 700,000+ died due to starvation and disease).
No-one knows exactly how many were killed in The Holocaust by the Nazis due to the Moral Guardians kicking up a fuss whenever someone tries to find out, but up to 16 million is the highest current estimate. This number does not include all the civilians killed directly or indirectly by Nazi Germany's troops.
As Stalin's biggest fan, Albania's former communist dictator Enver Hoxha also carried out a number of purges during his time in office (albeit they were on a much smaller scale).
The French Revolution between 1789 and 1799 saw several Purges, some directed against royalists, some against 'dissenting' factions within the Revolution. The guillotine was introduced to make the executioner's workload more feasible.
- Same thing - but worse - happened after Red October. During the Russian Civil War, the Bolsheviks quickly executed some representatives of the old regime. As the months went by and the ensuing civil war intensified, the purge grew into a Reign of Terror. In fact, all the factions involved in the civil war (the White Army, the Anarchists, the Czech Legion etc.) conducted purges of some sort - though they had different targets. Oh, and it was a very mobile war. That is, sometimes this "shoot the previous Mayor, Town Council and anyone you don't like who happened to be around" routine was done repeatedly.
During the early first century BC, Rome went through a bloody purge when Marius seized power, then Sulla's proscription. About forty years later, the Second Triumvirate held their own proscriptions, referred to in Shakespeare's Julius Caesar. Later emperors' struggles with the senatorial order were frequently depicted as purges by historians.
Upon the death of Gamal Abdel Nasser in 1970, the Egyptian leadership decided that it would be best to let Vice-President Anwar Sadat run things for a while, figuring he would be a pushover if they wanted to oust him. By the end of 1971, most of his political enemies—both among the leadership and outside of it—were either dead or imprisoned, the result of an event known as the Corrective Revolution.
The origin of the word "decimate" comes from the practice of killing every tenth man, drawn by lots, in a rebellious city or military unit.
Kind of a feature of Chinese governments since the fall of the Empire of the Qing. Most notable would be the anti-rightist purge of the early 1950s, when the amnesty the Chinese Communist Party had afforded to all those who had defected to their cause in the course of the Civil War was ignored in favour of re-education camps and killing fields. About the same time came the National land reform, which saw particularly wealthy peasants being denounced as 'feudal' and 'bourgeois'; most if not all of said citizens' land and property was confiscated. Many of them and their families did not survive this process. There are no numbers for the number of defectors imprisoned/executed - it couldn't have been more than a couple of million - but we're fairly sure that about a million 'landlords' must've died at the hands of their neighbours under the Party's supervision.
The right-wing dictatorships of Latin America (such as Pinochet) in The Seventies did these fairly quickly.
General Suharto of Indonesia conducted a huge anti-communist purge campaign in 1965-66. Of course, this was mostly an excuse to eliminate political dissidents, and most of the purge's victims had little if anything to do with communism.
The numerous regimes modeled after Stalin's USSR or Hitler's Germany also conducted purges, though not quite to the scale of their "mentor" countries. After Stalin's death (1953) the purges in East Europe became less common and far less brutal (people usually lost their jobs instead of their heads, or were put in prisons rather than labor camps).
For a long period of history in the Ottoman Empire, a Sultan's sons would compete for the crown amongst themselves by slaughtering their male siblings (and sometimes nephews and uncles.) Whomever was left alive at the end of the purge was declared the new Sultan. (This lasted until the Empire finally got into the habit of declaring the firstborn son the next ruler.)
Ivan IV "The Terrible" accused the top Boyars of trying to reduce him to their puppet - he seized actual power in the wake of a big riot against them. Later he moved out of Moscow with some favorites and issued what amounts to ultimatum: he gets to "set aside" some land as royal personal property (a pre-existing mechanism, but not intended to manage confiscations or keep servants above the law) and sort out "the traitors" (list attached) - or abdicates. If this oligarchy did see fit to steal from the crown prince or refer to a minor noble as "slave", one can only guess how they treated common people... So the monarch got support of pretty much everyone else. Cue raids, confiscations and exile of heirs to the borders. The purge dropped in popularity when some participants reduced it to plain "Rape, Pillage and Burn" deal. Also the folk from confiscated (i.e. best) lands ran to the borders: instead of "devil you know" they may get a favorite of the worst sort, and even if not, this voided various lucrative arrangements. The more people ran, the more infrastructure failed, so more ran - until this led to two lost wars. After which Ivan IV fixed some problems his purge created... and purged his troublesome servants too for good measure.
The Viet-Cong had a long drawn out purge, in which they ordered hits not only on informants but on anyone who might be inconvenient to them including absentee landlords, but also village headmen, journalists, artists, athletes, and any other figure of social regard that was suspected might have sympathies that could make them an opposition leader.
Similarly the nebulous Army mafia of pre-ww2 Japan controlled Japan by assassinating politicians. Bringing on what amounts to a Japanese version of a Day of the Jackboot.