Better the Devil You Know

""You destroyed the demon! Yin and yang! Now the world is out of balance, nobody told you to destroy the demon! Now there is a void for a new, stronger evil to fill!""

- Uncle, Jackie Chan Adventures

Finally, after a long struggle, our heroes have managed to defeat the Big Bad, but wait—they can't just kill them. That would be terrible! Because as soon as you kill the Big Bad, something else will come along to take his place. Maybe The Man Behind the Man shows up, or maybe the Sorting Algorithm of Evil kicks in. Maybe the Balance Between Good and Evil means that someone else will just become the new Big Bad, or maybe it's just Inherent in the System, but the fact you've won doesn't mean it's over.

Sure, the Big Bad may be evil, but at least as long as he's around, you know what you're up against. You know his weaknesses, you know how he thinks, and you know how to deal with him. And you know what he won't do. But if someone new takes over, suddenly you're right back to square one and you have to figure out how to beat them all over again.

If the Big Bad actually does get dispatched despite this, the heroes may soon find themselves wishing for the return of the old Big Bad, and in extreme cases, may even try to restore him to power. (If possible.)

Related to We Want Our Jerk Back, Friendly Enemy, and Worthy Opponent. Bread and Circuses or Villain with Good Publicity may also invoke this trope if removing the Big Bad will cause public backlash, or the heroes may fear an Evil Power Vacuum.

Anime and Manga

 * Gurren Lagann invokes this to an extent after the seven-year Time Skip: the tyrannical Lordgenome has been deposed, but his cryptic prediction upon his death comes to nightmarish reality as the Anti-Spiral invade and prove to be a far more powerful and terrifying threat than Lordgenome ever was. Lordgenome may have oppressed humankind, but it turns out he did it to protect the world from the Anti-Spiral, who seek to destroy humankind.
 * Arguably, this is the World Government's feelings toward Whitebeard from One Piece. Sure he's a badass pirate, one of the strongest in the world, but when he's killed, the general populace is screwed over..

Comic Books

 * In the Marvel Comics storyline Infinity War, Adam Warlock has been captured by his Enemy Without, the Magus, who is minutes away from reactivating an artifact that will give him godhood. Then, they're attacked by Doctor Doom and Kang The Conqueror, who naturally want this artifact for themselves. After a moment's hesitation, Warlock begins helping the Magus against the would-be usurpers, telling himself "Better the devil you know..." And what devil could you know better than the one who's part of you?
 * Every time Doctor Doom is deposed as ruler of Latveria, the guy who tries to replace him is even worse, and when he inevitably returns, the citizens of Latveria are glad to have him back. Even Spider-Man was forced to admit he's a better ruler than any alternative.

Film

 * In the third instalment of Tremors the inhabitants of the valley keep a huge carnivourus subterranean worm alive, because the'd already learned how to avoid it, while its presence should stave off the real evil - the real estate agents!

Literature
"Booster: "Better the Hutt you have tagged than one you don't""
 * In For Love of Evil from the Incarnations of Immortality series, Satan is deposed after singing a hymn during the climax of the previous novel (long story). The most evil person on Earth is automatically selected as his replacement, and turns out to be far, far worse than Satan ever was. He gorges on food, rapes the damned child souls, and bullies Hell's staff around instead of actually governing Hell and keeping track of the Celestial Bureaucracy, which is Satan's responsibility. Also, Satan is really nice, while this guy is a complete asshole.
 * In the Discworld novel Carpe Jugulum the old Count Magpyr was far fairer to his opponents via Contractual Genre Blindness, respected his Igor, and much preferred by the townspeople he terrorized. So, the heroes usurp the upstarts with their older, known adversary.
 * Animorphs did this once when a Yeerk inspector came to Earth to see why the invasion was taking so long, and would have taken the Visser's place once the Andalite bandits had been taken care of. The Animorphs end up killing the inspector so Visser Three stays in charge; "better the evil we know and makes stupid mistakes than the one who doesn't."
 * This is also their logic for not wanting Visser One to take over the Earth invasion again---which, of course, she proves by figuring out they're humans. Somewhat subverted, however, in that Visser One wants a slow, secret infiltration of the planet while Visser Three wants to declare all-out war and kill millions or more people, so that the Animorphs have to balance Yeerk politics to get Visser One's methods while keeping Visser Three the person in power.
 * In The Dresden Files Harry's description of 'Gentleman' Johnny Marcone tends to show some shades of this. Sure he's a powerful crime lord that turns a profit on almost any crime in Chicago, but Marcone has known limits. The gang-wars that would likely replace him aren't as knowable as he is.
 * Used in one of the X-Wing books as the reason not to execute a known spy. In typical Star Wars tradition they messed with the original idiom.

""Better the Moff you know than the Emperor's new envoy.""
 * Another character puts it differently.


 * Attempted in the New Jedi Order novel Rebel Dream: Wedge's plan for the Siege of Borleais is to maneuver the fairly lackluster enemy general into a series of indecisive engagements, with the overall goal of buying time for various covert plans to take effect. Unfortunately, after the Republic wins a major military victory they don't want, the Yuuzhan Vong return in force, led by Czulkang Lah, father of the warmaster and undisputed Old Master of war.

Live-Action TV

 * Hogan's Heroes. Several times Hogan and his men had to intervene to save Colonel Klink from his folly, because any other German officer who replaced him would be more effective in stopping their activities.
 * This seems to be the philosophy of the Tok'ra and probably goes a long way towards explaining their distinct lack of progress over the millenia.
 * And they're right: when one Goa'uld starts to get power over the others (Anubis and Ba'al come to mind), things get much, much worse for our heroes...and the galaxy at large.
 * The episode where they try to sabotage the meeting between Apophis and his nephew Heru'ur, both of whom are powerful System Lords, they accidentally cause Apophis to kill Heru'ur and absorb his armies and fleets. In retrospect, an alliance between the two would've been a much more preferrable, as each would constantly try to off the other, due to their Chronic Backstabbing Disorder.
 * Invoked word-for-word in The Thick of It by Stewart Pearson, when Cal "The Fucker" Richards descends on the Opposition. Also implied when is forced out by.
 * Blake's 7. Blake refuses to kill Travis. "...as long as he's alive, he'll be the one chasing me. And I know I can beat him."
 * On Jack of All Trades, Jack and Emilia often wind up helping Governor Croque to keep his job, mostly because his likely replacement would be much more competent.
 * Inverted during the Dominion War on Star Trek: Deep Space Nine. While the station is occupied by Cardassian and Dominion troops, Kira and Odo try to play Gul Dukat and Weyoun, commanders of the two factions, against each other. Kira explicitly notes they're better off trusting the devil they don't know—because the one they do know is Gul Dukat.
 * The old Robin Hood TV show (in black and white) specifically had an episode very late in its run that was titled this. The episode involved the Sheriff of Nottingham being replaced with a much more cunning and immoral man. Robin even commented on the fact that they had been able to depend on the regular Sheriff being only so evil and still following the law when pressed. The new guy? not at all.
 * Power Rangers Zeo: In "Mondo's Last Stand", after the Rangers defeated Mondo, they believed they'd no longer have to face monsters for a long time. Their peace only lasted until another villain took over the Machine Empire.
 * El Chapulin Colorado once helped a woman who invoked this trope to justify accepting his help instead of Supersam's.

Professional Wrestling

 * During the Invasion storyline, Vince McMahon Hangs a Lampshade on this trope by name in an attempt to coax The Rock into staying with the WWF.

Web Comics
"Kevyn: Ennesby, Get out of there. We're supposed to be growing a fresh A.I. for the ship, not giving you a new home. Ennesby: Hey, look at it this way: If I leave, you've got to grow, train, and befriend an unknown quantity. Ennesby: But if I stay in here, you get a ship that already likes all of you well enough to hang around while getting shot at."
 * The "War in Hell" storyline of Dominic Deegan sees Dominic fighting on behalf of the Demon Lord Karnak. Not because he wanted to, but because his family literally knew Karnak before his demon days, and as a result knew how to handle him. Any other demon lord securing power would have meant a lot of trouble.
 * That, and Karnak was linked to Dominic's friend Szark through the wound he inflicted on Szark in his youth. If Karnak bit the dust, so would Szark, and Dominic, fresh from his victory over the Storm of Souls, was determined to do everything in his power to protect Szark, "Fated Fatal" be damned.
 * Schlock Mercenary on ship AI (they did have some problems with this both before and after):

Western Animation

 * Jackie Chan Adventures did this. Season 1 focused on the demon, Shendu, as the Big Bad. At the very end, Jackie defeats Shendu, putting him in statue form, and Jade blows him to pieces with one of his own talismans. This is apparently a bad thing as Uncle tells him that now Shendu's been destroyed, a new, much worse evil must take his place. The second season then deals with the spirit of Shendu, after taking over Valmont's body, trying to reopen several demon portals so that his demon siblings can escape and wreak havoc on the mortal world.
 * A Broken Aesop for the rest of the series, though; after Shen-Du and his siblings are defeated they are replaced as Big Bad by Dao-Long Wong, who is bad but not as bad as Shen-Du, who ultimately returns and steals his thunder in the finale`; when Shen-Du is defeated by sealing him in his statue again, this time he isn't destroyed because they remeber Uncle's sage advice....except that the new Big Bad is Tarakudo, King of the Shadowkhan and Lord of All Oni, who is the only villain out to single-handidly conquer the entire planet and very nearly succeeds, so his advice was completely subverted. Tarakudo is followed by Shen-Du's son, who is dangerous than Dao-Long Wong but not really as threatingg as any of the other major villains either, though in this case Tarakudo ended up in Shen-Du's position in that he was sealed, but not destroyed, so he at least follows Uncle's metarules.
 * Lampshaded in The Spectacular Spider-Man. After Spider-Man takes down mob boss Tombstone, Captain Stacy tells him that he's just created a power vacuum in the underworld, and that "nature abhors a vacuum".
 * Subverted in ReBoot. After Daemon is stopped Megabyte comes back to Mainframe. Dot and Bob refuse help from the Supercomputer because they have dealt with Megabyte before and know how he operates. This bites them in the ASCII when Megabyte doesn't operate like he used to, giving up on conquest and going for personal revenge instead. He ends up taking over the Principal Office in one episode. Since the series ends on a cliffhanger here, it looks like Megabyte won.
 * There is a follow-up web comic that continues, Paradigm Lost.
 * Following the chaos resulting from "killing" the Shredder the 2K3 Ninja Turtles temporarily ally themselves with Shredder's adoptive daughter to ensure that the Foot Clan gains dominance in the gang wars. Leonardo, invoking this trope word for word, reasons that as bad as the Foot may be, putting them back on top would end the massive gang wars and get some order in the city.
 * This is why you don't defrost the old leaders of Miseryville in Jimmy Two-Shoes. Lucious von Heinous the VI Ith might be the devil, but compared to his dad, grandfather and great grandfathers way back down to Lucious von Heinous the Ist, he's pretty much the best of a bad situation.
 * Slimer and The Real Ghostbusters episode "Out with Grout" featured Mr. Grout, the bossy manager of Hotel Sedgwick, leaving the job to become the manager of the new Uptown Hotel, much to the (temporary) relief of Slimer and Buddy. When wannabe ghostbuster Professor Dweeb became the new manager, they decided to bring Mr. Grout back, since he at least ignores the ghosts rather than trying to bust them.
 * Potsworth and Company episode "When Bubba Rules" featured the Nightmare Prince's mother demoting him and hiring another villain. Despite knowing they'd have to face a new enemy, the heroes were happy they'd no longer have to worry about the Nightmare Prince. However, once they tried to stop the new villain, the heroes decided to trick the Bigger Bad into firing the new villain and reinstating the Big Bad.
 * In one episode of Jumanji, Van Pelt explained that he hunts because, in Jumanji you either hunt or are hunted. Peter, Judy and Alan then decided to hunt Van Pelt. When it seemed they got rid of him for good, Jumanji turned Peter into a new Van Pelt. The episode ended with Peter going back to normal and Van Pelt being back.
 * The Fairly OddParents episode "No Substitute for Crazy" featured a substitute teacher named Ms. Sunshine. When she sadly reminded the students that, as a substitute, she'd have to leave as soon as Crocker got back and suggested the only way to stop that would be someone with a magic wand making her the new regular teacher, Timmy wished for that. In the next day, she revealed her true colors: she's a fairy hunter named Ms. Doombringer and was so more competent that Crocker Timmy ended up wanting Crocker back and having to leave the giant butterfly net she placed at the school area to wish for that.
 * Also, that episode's Brazilian title is a variation of the trope's name replacing "Devil" with a word that means "Crazy".
 * A Tiny Toon Adventures episode had Buster and company fearing this trope when Acme Looniversity Vice Principal Yosemite Sam applied for a job at another school. Out of fear a more competent person would take the job, the Tiny Toons sabotaged Sam's efforts.
 * When the Stunt Dawgs dispatched Fungus away, they didn't expect Airball to take over and make things so worse they'd bring Fungus back.
 * At the opening of an episode of The Simpsons, a billboard with an ad for Quimby's campaign describes him as The Devil You Know for 18 years.

Video Games

 * Lampshaded by name in StarCraft to explain why the heroes of the story were working with Kerrigan ("Queen Bitch of the Universe," in her own words, and leader of an alien locust swarm) of all people to fight the UED. - a dictatorship lead by Space Russians from Earth, who's only contact with the heroes so far have involved bullets.
 * The first half of Brutal Legend sees Eddie Riggs help out rebel leader Lars Halford, who's trying to free his people from the tyrannical rule of General Lionwhyte. They succeed, but the instant they do Emperor Doviculus turns up,, and shatters the rebel army. Turns out Lionwhyte was the only guy able to convince Doviculus not to just Kill All Humans.
 * In Metroid, the eponymous monsters are pretty nasty, but in Metroid Fusion (where all Metroids but one have been exterminated, that one being in captivity) it is discovered that Metroids were developed my the Choso to prey on even more dangerous alien beasts called X-Parasites. Kind of like how mongooses were introduced to India to get rid of snakes. Now that the predators are gone, their prey is more dangerous than ever.

Real Life

 * Many animals have a defense that is designed to cause severe discomfort to their natural enemy, but rarely kills (for example a skunk or porcupine). The result is, the predator remains in the area, and they keep other predators out of their territory, but the predator remembers what happened the last time, so the skunk can now feed in peace.
 * Allegedly a factor in the Russian revolution: because foreigners were supporting the white army, support grew for the red army, which wasn't influenced by unknown, foreign powers. Of course, the fact that the Red's revolutionised propaganda and used that to play that angle didn't hurt, either.