Knight of Cerebus

""Irresponsible children. My patience is stretched miles beyond its threshold. Embrace your wounded; you will be joining them in hell.""

- The Wanderer makes his entrance, It's Walky!

In order to add more drama to a series which has been, up until that moment, lighthearted and comedic in nature, a villain is introduced (usually the Big Bad, but may also be The Dragon of the series) which is played completely straight, in contrast to the bumbling and comedic villains the heroes have faced before.

This villain's arrival is usually heralded by a sudden downturn in humor, as well as several Kick the Dog moments (up to and including killing off recurring characters) to show the audience this guy means business. In other words, a catalyst for a drastic change in mood toward the dark and dramatic.

In some depictions, particularly Lighter and Softer ones, said villain may still have some light hearted or comical traits, but still gives a much higher sense of dread and genuine threat to the heroes than previous adversaries. Some cases of the trope may be harder to define by comparison in a particularly ineffective Rogues Gallery, though a clear cut example at the very least can actually place the protagonist in real danger compared to the Harmless Villain that poked his poodle in a previous arc.

A typical symptom of Cerebus Syndrome. A Knight of Cerebus is very likely to be Dangerously Genre Savvy, but also runs the risk of becoming a Villain Sue. Arguably a subtrope of Threshold Guardians. See also Dead Serious, Not-So-Harmless Villain. The show may Shoo Out the Clowns first. Often, this results in a case of Vile Villain Saccharine Show. When this kicks off Cerebus Syndrome, his arrival is a Gut Punch.

Anime and Manga

 * Rosario+Vampire's Monster of the Week formula progressively stopped being the main formula due to these three:
 * Kuyo and his student police force,.
 * Ruby's master helped the transition along, in an arc that !
 * Midou and the outcast monsters,  After this incident, the main theme of Fantastic Racism between humans and monsters, and between monsters and other monsters, really began to take over.
 * Legato from Trigun. See his entry under Gut Punch for more detail.
 * Monev follows Legato's cue and begins shortly afterwards - while previously Vash was always able to stop the villains before they can do serious harm, the guy basically moves down everyone in his path (including women and children) to get his target - and he actually enjoys this collateral damage. This is also the first time that Vash really loses it, and comes close to killing Monev.
 * Saito Hajime in Rurouni Kenshin. His introduction signalled the arrival of the Kyoto Arc (and the much more dangerous villain Shishio) whereas previously, the series had been a light-hearted action comedy where, a few serious villains like Jin'e and Aoshi aside, Kenshin's everyday life was a light-hearted and comical romp.
 * from Digimon Savers is the perfect example of this trope. Before he had appeared the only real "dark" parts of the anime resulted from Gotsumon's incredibly hostile attitude toward Ikuto/Keenan. When  arrived, he brought genocide (including the deaths of both of Ikuto/Keenan's "parents", resulting in genuine Tear Jerker scenes) and singlehandedly made the entire season the darkest one yet. Not to mention the fact that for once we had a genuinely evil, and also BY FAR the most evil character ever to grace the franchise.
 * Devimon in the original Digimon Adventure. While the first few episodes of the show were simple Monster of the Week, his appearance in Episode 8 introduced a proper, intertwined story arc and highlighted that the show wasn't kidding around anymore. It got somewhat lighter - though with even more Myth Arc - in the short 'Etemon arc' - only for Myotismon to firmly seal the series in Cerebus Syndrome.
 * While Digimon Tamers was always more serious and thinky than the other series, Beelzemon's arrival causes a big shift. Darker and Edgier went from meaning "Digimon don't automatically respawn at the Primary Village anymore so fights actually count" to . Things got a little bit bleak at that point. They still forgave Beelzemon. Eventually.
 * Whenever Medusa shows up in Soul Eater, things stop being whacky and people start dying and going insane.
 * It's pretty much both at the same time when any major antagonist is around, with varying amounts of seriousness and death.
 * Asura might be an aversion, as he's so insane that he sometimes circles all the way back into funny. At the same time, that weird dichotomy sometimes makes him even more disturbing. (considering the clown=insanity motif going on, it makes sense.)
 * Zophise from Gash Bell. Gash Bell tends to get a lot of these, because most of the enemies tend to be fairly goofy, it's jarring when you get someone who's playing for keeps.
 * Tao Pai Pai, and Piccolo Daimao from Dragon Ball.
 * Raditz in DBZ, who jumped the series out of being comedy-focused altogether.
 * General Rildo in Dragon Ball GT; until he showed up, GT was a throwback to the comedy of early DB.
 * Mazinger Z has a weird example in Count Brocken. To put it simply, he is the first villain to harm(and actualy killed) innocent people. And from that, he proceed to do some horrible stuff. He is so notable amongst the villains that in fact, right in this wiki, he is the most notable person that is mentioned when the Dark part of Mazinger Z is talked about, complete with arguably creepier design than the already creepy Ashura and the show indeed goes into the darker parts after this. The weird part ? at the same chapter he appeared, he provided the single most hilarious moments in the entire series in a rather stupid way. Its kinda hard to think hes the same person who killed person on the screen for the first time.
 * Fate Averruncus from the Mahou Sensei Negima manga. His first appearance saw him . When he appeared a second time he brutally averted Bloodless Carnage by  . This was the trigger that eventually led Negi to begin using Black Magic. Oh, and Fate's ultimate goal is
 * Arguably, serves as an earlier example. Once it's revealed that, the series started its Genre Shift from harem comedy to shonen.
 * Fate Testarossa of Magical Girl Lyrical Nanoha is another Fate that served as this, shifting the focus away from the standard Gotta Catch Them All, Monster of the Week, Magical Girl format upon arrival and eventually sending the plot careening towards a more interdimensional scale.
 * No mention of Precia Testarossa? Nanoha really went dark (but possibly substantially improved as well) when she was introduced. How exactly was she introduced? After she left, it became slightly lighter again for the later two seasons.
 * At least until Jail, in the third season, mentioned that he had all of the Numbers (functonally, and sometimes biologically, his daughters) impregnated with clones of himself. Yeah...
 * The Huckebein from FORCE are taking the series to a new level of dark.
 * Mukuro Rokudo from Katekyo Hitman Reborn is an example of this trope; in the beginning of his story arc, a number of major characters are badly beaten. His appearance also signals a major Genre Shift in the series, which had been comedic until this point.
 * Makubex in GetBackers. Before the IL recovery mission, Ban and Ginji were retrieving things like expensive melons and a blind girl's violin. Makubex threatened them with an atomic bomb!
 * Then came the true arms of Venus and all that, but Makubex was the first to give them a real battle.
 * Takasugi Shinsuke in Gintama is the first seriously evil character, and is featured in the series' first serious arc, benizakura. He is probably also the only main character in the show who doesn't have comedic side.
 * Unless he's hiding something behind that cute face and mindless violence, Kamui counts.
 * Though Tsutomu Nihei's Blame! was never what you'd call light-hearted, the appearance of The Safeguard marked a dramatic shift in the storyline to something much more epic.
 * Pantyhose Tarou was only the first of a succession of very serious, very powerful foes in Ranma ½: while earlier opponents were always ineffectual antagonists versed in wacky, fun, harmless Martial Arts and Crafts tournaments, Ryugenzawa's Orochi, Prince Herb of the Musk Dynasty, Ryuu Kumon, and The Phoenix King Saffron followed in Pantyhose Taro's footsteps by forcing Ranma & Co. into more serious, no-nonsense combat, where death was suddenly a very real possibility.
 * It should be noted, however, that Ranma ½ doesn't have overarching plots and the "Cerebus Syndrome" brought about by those characters only lasted for their specific story arcs, being more or less forgotten about once their arc is over (not to mention that their arcs aren't entirely joke free either).
 * In fact, Tarou is actually the least "Grimdark" of the series' Knights of Cerebus, as while a ruthless, formidable fighter, Tarou's stories also tend to be full of the usual goofiness and just plain ridiculous happenings. In his first story, the whole mess is over getting his name changed, while his last story has him battling a fellow lucky Jusenkyo victim over back-pain relieving magnets, which he ends up believing will give him the power to Take Over the World.
 * Gundam ZZ started out almost ridiculously lighthearted but after a bunch of Ineffectual Sympathetic Villains, Haman Karn gets into the plot and all of a sudden the heroes really need to worry.
 * Another Gundam example would be G Gundam though only the first few episodes are rather easy going until Devil Gundam and Kyouji are first mentioned.
 * It's still relatively easygoing even after the introduction of Kyouji and the Devil Gundam, but then Master Asia (or, more specifically, his ) jumps into the story...
 * Princess Tutu starts off as a fairly light, straight-up Gotta Catch Em All Magical Girl series for the first few episodes. Then Princess Kraehe steps in and BAM! -- here comes the Genre Shift.
 * Depending on if we're talking about the manga or the anime of Rozen Maiden, either Barasuishou or Kirakishou counts. It should be noted in Kirakishou's case that when, you know there won't be much more comedy. Barasuishou on the other hand , and with her dead serious attitude that everybody must participate in the Alice Game, it is not very surprising.
 * Butch and Cassidy of Pokémon seemed to be headed for this at their first appearance, being a Terrible Trio in their own right with a crooked Officer Jenny. It...didn't last long, but at least other members of Team Rocket manage to stay properly intimidating—especially when they show up in force. Even Max admits that the cast is pretty lucky that they usually only have to deal with the Terrible Trio that stalks them around.
 * Pokémon Hunter J easily surpasses them in malevolence, being the darkest villain to ever appear in the series and to never suffer from Villain Decay, not to mention being one of the few characters that was actually . While technically not a villain, Paul seems headed this way, being more abusive towards his Pokémon than anyone else.
 * Another good example is Sabrina, who popped up MUCH earlier than Butch and Cassidy and WAY before J did. Sabrina only appeared for three episodes, and after her arc everything returned for normal, but for years later, no villain surpassed Sabrina in terms of scariness. Let's face it: she transformed you into dolls after she beat you, and was just plain creepy. J may be more evil and has no qualms committing murder, but at least she doesn't turn you into a doll!
 * Combining this with Not-So-Harmless Villain is Team Rocket themselves in the Best Wishes series.
 * Yubel in Yu-Gi-Oh! GX. After her appearance, Idiot Hero Juudai starts his downward spiral, characters start dying and some of the standard humor in the series begins to disappear as the series takes its turn towards full Deconstructor Fleet territory.
 * Evangelion was a dark series to begin with, but the events of the "Action Arc" (from Asuka's arrival up to Leliel/Twelfth Angel) were relatively light-hearted, with Misato and Kaji seemingly making amends, and Shinji starting to gain some confidence. ...Then came Bardiel/The Thirteenth Angel, and everything went to Hell, culminating in End of Evangelion.
 * Rebuild of Evangelion 2.0 is, for most of its running time, a much Lighter and Softer story than the episodes it's adapting. There's a good amount of comedy, we see the kids bonding, Asuka's less of a Jerkass, and the angel battles ("Clockiel" and Sahaquiel) are focused more on awesomeness. Then Bardiel shows up and possesses Unit-03, and the movie goes straight into Nightmare Fuel territory.
 * When Fiore shows up, she starts off as a cute Ineffectual Sympathetic Villain working behind the scenes.
 * Medaka Box once was a lighthearted, comedic series about school adventures of a God Mode Sue and her harem. After 14 chapters of that, the first serious antagonist, Unzen Myouri appeared, heralding oncoming Genre Shift into a fighting series with a brutal bloodbath (no one supposedly died, but a ton of people probably were put in hospital for years). And just as the arc, started by Unzen's appearance was about to end, Kumagawa Misogi stepped on the scene, signaling a lesser shift to even more Darker and Edgier tone.
 * Chirin no Suzu was all cute and adorable until the Wolf appeared and the mood became very dark.
 * Puella Magi Madoka Magica looked like it was going to be another typical magical girl show, albeit one with unusually dark undertones. Then came Episode 3, which introduced Charlotte, the third Witch. The moment when she was the moment when the series showed just how dark of a Deconstruction of the genre that it could be. And this was only a taste of what would come later.
 * Unusually for this trope,
 * The Spin-Off manga Puella Magi Kazumi Magica has . Another unusual example because she only took the role in the fourth chapter, having appeared as a Mysterious Watcher in the first two and an easily defeated antagonist in the third. But in the fourth, hoo boy...
 * Claymore never made any pretenses to be anything other than a dark series, but whenever  turns up, things are going to go south very, VERY fast.
 * Mag Mel from Bakugan. Previous villains were dark, but Mag Mel is by far the most terrifying villain yet with an extremely dark storyline. He was imprisoned for genocide and that's before the series even started! Once he appeared, he Mind Raped Dan and Drago in a very horrific manner. Once he was finally free, he started trying to burn Gundelia to the ground. In scope of sheer evil and darkness, he's the darkest and most horrifying villain in the entire series!
 * Bleach has Aizen. In the Arrancar Arc, there's relatively little comic relief compared to the last two. And the man has no sense of humor himself. His reaction to SEEING comic relief unfold is to wonder whether or not it's a bad strategy to take him off of his guard.
 * Shukuro Tsukishima was this during the Xcution arc.
 * In the "Thousand Year Blood War arc", it is heavily hinted that  will become this.
 * How do we know this
 * Technically Byakuya and Renji were this as they were the first enemies to defeat and nearly kill Ichigo.
 * The true knight of Cerebus in the series is one unseen Vandenreich member
 * The entire first episode of Cubex Cursedx Curious seemed to be setting up for a lighthearted Slice of Life comedy series. Episode 2, enter: Peavey.
 * Higurashi no Naku Koro ni seems like a light-hearted harem comedy until pops up and starts putting things in Keiichi's head.
 * Tiger and Bunny has several, each one putting the series deeper into much darker territory:
 * Lunatic. A Vigilante Man, he's the first character who kills somebody in the series. Whenever he shows up, things starts turning grim..
 * Jake Martinez. While Lunatic was treated seriously, he was at least a Well-Intentioned Extremist, while Jake  For the Evulz. He was the first villain who was shown to take pleasure in evildoing.
 * from episode 15, who have been indirectly responsible for starting a chain of heartbreaking moments that prevailed through the rest of the series.
 * And finally the Big Bad  who who quickly learned himself a place on Complete Monster page with.
 * Space Monsters from Gunbuster - for the first two episodes series is lighthearted and funny, being basically sport story with mechas and serious elements were nothing more but backstory. Once the first battle has come, it turned into desperate fight for survival and stayed that way even after the shift to the Super Robot Genre.
 * Diebuster starts as sympathetic and optimistic Super Robot Monster of the Week show, but after one of  shows up, things go to hell very fast.
 * Phi Brain: Kami no Puzzle played with this - new villain, Herbert Müller, while a Complete Monster, didn't started the shift to more serious tone. In fact his apperance stopped one that was already taking place, by putting delay on plans of previoriusly estabilished villain, who resumed them after Müller was out of picture and became Knight of Cerebus himself.
 * It's interesting to watch the increase of the power of the villains in One Piece. Alvida and Morgan possessed no real threat to Luffy, and Buggy wasn't really much of a challenge either. Afterwards, Captain Kuro and Don Krieg were much more menacing, but still relatively weak: They were just bad guys who happened to show up at the time. Everything changed when Arlong came along, and while the series retained its light-hearted tone for the most part, seeing what the stakes are when a real monster gets involved changed the world of the series forever. Follow this up with an enemy Luffy can't fight in the form of Smoker, and it's clear that the end of the East Blue saga was when the series hit its' stride.
 * And then Crocodile, Nico Robin and the Alabasta arc up the ante, going from relatively minor conflicts to an all-out civil war. It also marks the point where the heroes start ending up on the verge of defeat (repeatedly) by an opponent far beyond their level, as well as expanding on the series' Myth Arc (becoming far more than Luffy searching for some buried treasure and becoming King of the Pirates.)
 * Admiral Akainu finally averts the "Nobody dies in One Piece outside of flashbacks" rule  Blackbeard follows it up soon after by
 * Transformers: Beast Wars II is an incredibly light-hearted show with hilarious characters, that hardly ever takes itself seriously. And its villains are no exceptions - Galvatron - the Big Bad is a narcoleptic who spends most of the show asleep, leaving his inept kid brother Megastorm to run the show with an effeminate wannabe (Starscream), a thug who can only repeat his own name (BB), and Beavis and Butt-Head (Thrust and Dirge) under his command. Cue the last 10 episodes of the show, where Galvatron wakes up, takes command, and we learn that he has a gigantic Doomsday Device en route to Gaia, which he intends to use to destroy the whole planet and siphon the Anglomois energy. And then things go grimdark... Gigastorm (Megastorm after his makeover) is fatally wounded and dies in Galvatron's arms, and the whole series ends with
 * In Naruto, although the first major villain, Zabuza, had already been introduced (he more or less explains to the audience that being a ninja is dangerous work, if heroic) we saw the kids handling on their own against him with the help from their teacher, Kakashi; when Orochimaru is introduced, he is shown to be a villain that even the most experienced jounin fear and ends up killing the Third Hokage. Much later, the reveal of Pain serves as this since shortly after his introduction he kills Naruto's bumbling master, Jiraiya.
 * Much like it's Spiritual Successor Claymore, Berserk is nothing short of a Dark Fantasy series. However, the TV series is considerably Lighter and Softer than its manga counterpart, so for the majority of the TV series' run, it was basically composed of Guts and Griffith talking about dreams and ambition, the Hawks battling the Tudor Empire for the Kingdom of Midland and a bunch of political stuff, and developing characterization that wasn't derailed by Adaptation Induced Plotholes or Adaptation Explanation Extrication. But when Nosferatu Zodd was introduced with his prophecy halfway through the series, followed by the introduction of the Godhand toward the end, we knew that this series was going to end on a bad note.
 * Over the course of the first half of Mon Colle Knights, the heroes had no problem repeatedly beating back the Laughably Evil Villains Out Shopping Count Collection, Bacchi, and Guuko. Then Dark Angel Zaha shows up and turns some of the heroes' monster friends against them by brainwashing them. And if that's not enough, there's Reda, a Dangerously Genre Savvy Dark Angel who is so powerful that even Shiru has problems with him, and he . Oh Crap...
 * The Metarex in Sonic X fit this trope really well. So basically, the first two seasons of the show were pretty much light-hearted and funny in tone. Then cue the arrival of the Metarex, a group of dangerous cyborgs and robots that plan to harness the power of the Planet Eggs to . The Metarex come in many different types of their own, like the one-shot villain Red Pine, the Laughably Evil brute Yellow Zelkova, emotionless Complete Monsters like Pale Bay Leaf as well as Black Narcissus, who captured and tortured Chris and Cosmo and used them as bait to lure Sonic to him, and the tragically villainous Magnificent Bastard Dark Oak himself.
 * Fairy Tail has two. Jellal is the first villain who poses a serious threat to the cast's lives, and is trying to return Zeref himself, as opposed to the various demon Zeref created that have been sought out in earlier arcs, or power skirmishes that have otherwise been the focus. In adition, while previous tragic backstories have been about losing or fighting with family members, his and Erza's past is full of all kinds of slavery, torture, and betrayal. After Jellal every arc is some serious threat that will either kill the cast or destroy the country. The second is Hades, who is also the second villain to seek Zeref. He turns the first lighthearted arc in over 100 chapters into a fight for survival that ends with the series no longer being a Nobody Can Die story, many characters' sufferings to turn out to have been for no reason, Zeref potentially unleashed on the world, and he . Zeref himself, oddly enough, has yet to invoke this trope.
 * In the Monster Rancher anime, General Durahan's arrival signaled the end of lighthearted episodes; he even appears right after a lighthearted one. He's also a literal knight.
 * Toriko was a light hearted food hunting series with the occasional creepy GT Robots, and the arc after them is another finding secret recipe mission much like prior to their appearances. then Tommyrod shows up. Unlike Starjun and Grinpatch, who were Noble Demon and Affably Evil villains respectively, Tommyrod was a Complete Monster who literally kept all kinds of hideous parasitic insects within his body, who seriously tries to kill Toriko, and from there the story gets much darker.
 * Starjun is a milder example, being no-nonscence and having a dark aura, and being the truly first time that.
 * Tengen Toppa Gurren Lagann has Thymilph, who, though he ended up tame compared to Lordgenome and.

Comic Books

 * Cerebus didn't actually have one of these; the major turns for the Darker and Edgier usually (but not always) involve the scary-as-hell matriarchal fascists called Cirinists, but there's no one character that fits the bill.
 * During the 90s comic book phase of 'grim and gritty', DC's Justice League was played for laughs by Giffen and DeMatteis until the arrival of Despero in JL #38 and his subsequent killing spree (including killing a team member's parents) and introducing a new 'serious' phase in the history of the book... whose readership then tailed off.
 * And with the advent of Infinite Crisis Justice League ally Max Lord was retconned into being one of these. His recent return as a White Lantern ramps this Up to Eleven.
 * The supervillain Harm in Young Justice; the first page of his first appearance is marked by Arrowette, bloodily impaled with one of her own arrows, saying "But that's n-not funny..."
 * Willy Pete in Empowered gruesomely killed a bunch of people by literally raping them to death (which is all too easy for him to do, as he is a fire elemental who cannot shut off the powers that make his body superhot) in his very first appearance. Note that we're talking about a comic book that was almost purely comedic up until this moment.
 * Note that since he is a fire elemental, his raping them to death
 * Ninjette's pursuers, while having their moments of black humor, ventured firmly into this territory when
 * Scott Pilgrim is a Wickety comic, and starts out very happy until Gideon shown up and.
 * To a lesser degree, the Katayanagi twins also messed up the comic's quirky nature.
 * The appearance of the Anti-Monitor in Crisis on Infinite Earths was such an Up to Eleven example (just like everything else about Crisis On Infinite Earths) of this trope that he not only ushered in Cerebus Syndrome for the entire DC multiverse, but induced a Cosmic Cerebus Retcon upon its entire history. However, instead of taking the danger to a new level, he instead warped the fabric of reality into the Dark Age and all its Darker and Edgier '90s-ness, since no one since has ever been able to come close to either his threat level or evilness level.
 * Sonic the Comic, while becoming somewhat dark as the issues passed by, really started becoming dark once Super Sonic appeared. It got even worse when he separated from Sonic.
 * Archie's Sonic the Hedgehog comic similarly started out rather lighthearted, but Robotnik was gradually made more and more into an actually menacing villain, and as he did the general tone of the series grew darker, and the constant gags and attention to construction that fueled the early installments gave way to constant peril and at least one issue that was almost entirely traced. Then Robotnik died and the comic turned to high school relationship drama, and I'll leave it up to you what effect that had on the tone of the series.
 * Les Légendaires uses this at several points to different level. The serie typically stars as goofy and comical, only to turn surprisingly dark and serious whenever the major villain of the current arc is introduced :
 * Darkhell is believed dead several time, but everytimes he shows up, it always ends up with people dying. Even more extreme, the flashback show that he did a lot of horrible things in the backstory : so far, almost everything bad to ever happen on Alysia has somehow a connection to him... no wonder he became The Dreaded in all Alysia.
 * While the Guardian was more of a Lawful Neutral type than an actual villain, his role as an antagonist in book 2 caused
 * While Skroa didn't really have time to cause much harm at his introduction in book 2, his come-back in book 7 and 8 caused a lot of death and almost led to . Spoilers about the next book suggest that he might do ever worst soon.
 * Anathos is probably one of the most extreme level; whereas the serie had already got quite serious and dark at this point, his appearance made the whole story goes even darker, starting with him
 * The Nodwick print comic, in order to move from the gag-a-week strips show in Dragon (magazine) into a Myth Arc, introduced one of these as a Big Bad: God of Evil Baphuma'al, who was a lot more competent and Genre Savvy than Dragon villain Count Repugsive (though, really, outdoing a villain whose first 'Evil Plan' involved going into the real estate business isn't that hard to beat...). Repugsive did get A Day in the Limelight in the print comic (where he ironically came closer to conquering the world than Baphuma'al did), but the plan was mostly Played for Laughs (it involved turning the universe into an 8-bit platforming game) and the heroes defeated him fairly handily..

Fan Works

 * Chaosgallantmon and Daemon from the Tamers Forever Series. When they show up you KNOW things just got serious.
 * Getting Back on Your Hooves had some sad moments in the beginning, but mostly a rather lighthearted story about Trixie trying to do exactly what the title says...Then Checker Monarch enters the picture. Word of God states her mannerisms were based off those of a Sociopath if that's any indication. Example? That was only her second appearence.
 * initial appearance in Ace Combat: The Equestrian War ends with her breaking Medley's wings and causing a Heroic BSOD to Rainbow Dash.
 * A few chapters earlier, Black Star. When he stated that only Firefly was able to fight him equaly, he wasn't making it up.
 * The arrival of the Benefactor's disciples in Challenge of the Superfriends: The End.

Film

 * The Boondock Saints is a series with lots of laughs along with the kickass action. But when Il Duce gets called in, things get serious very quickly.
 * When Darth Maul first showed up in The Phantom Menace, the movie got darker and it led to the death of a major character.
 * Thrax from Osmosis Jones.
 * Ed, Edd 'n' Eddy's Big Picture Show has While  only appears at the climax of the film, he changes many things in its short presence.  And that's not even the worst part:  Ouch.
 * The Toy Story series films has, who is anything but what his name implies.
 * Lord Shen from Kung Fu Panda 2. While the first film featured slapstick kung fu fighting and Bloodless Carnage, the sequel opens with Shen ordering a mass genocide, and then a few scene laters he rolls out what he's been inventing during the Time Skip—the cannon.
 * The Coachman from Pinocchio. And do you know how?

Literature

 * The David Trilogy and its titular character took the Animorphs series down a darker path than it had ever gone before, forcing its heroes to extreme measures in order to attain victory. While the series was never particularly lighthearted, the trilogy's aftermath saw the War Is Hell aspect really kick into overdrive, culminating in the last ten books.
 * Nihil from Brian Clevinger's Nuklear Age, who single-handedly transforms the story from a goofy, episodic, villain-of-the-chapter superhero parody into a tragic, post-apocalyptic drama. All of which is intended, by the author's own admission, as one huge joke on the reader.
 * The Denarians in The Dresden Files are literal Knights of Cerberus, and far scarier than anything that has previously appeared. Things tend to get a lot worse (particularly if you happen to be a Knight of the Cross and all around nice guy).
 * It's notable that a series as dark as The Dresden Files can even have Knights of Cerebus. After all, previous antagonists were a drug dealing warlock, psychotic werewolves, a ruthless and vindictive vampire, and an insane member of the fae. But none of them were as evil as the Denarians are.
 * And they're not even the worst this series has to offer. No, that title probably goes to The Skinwalker.
 * In the Codex Alera books, the Vord are definitely this. While they make an appearance in the first book, their importance grows quickly to the point where they become the Big Bad by the fifth, completely dominating the previous enemies.
 * While the newly-revealed backstory for the Ring made it obvious that The Lord of the Rings was going to have a darker tone than The Hobbit, this doesn't really hit home for either the reader or the characters until the introduction of the Nazgul, and especially of their true nature.
 * Harry Potter began getting Darker and Edgier from day one, but things start going to hell once Voldemort finally shows up at the end of Goblet.
 * The introduction of Dolores Umbridge in the following book didn't help - while not the most evil villain in the series, she's easily the most rage-inspiring among fans. As if that weren't enough, the same book also properly introduces Bellatrix Lestrange, an Ax Crazy Hero-Killer who quickly establishes herself as Voldemort's right-hand Death Eater.
 * The Yuuzhan Vong indirectly killed off Chewbacca, and Anakin Solo died fighting them. They completely destroyed the New Republic. The Star Wars Expanded Universe took a dark turn the minute they showed up and it has not been able to regain a lot of lightheartedness since.
 * Atlas from Percy Jackson and The Olympians is the first titan that the heroes fight, replaced the comedic one-shot villains that the heroes defeat during their journey with invincible skeleton warriors that constantly chase down Percy and his friends, and his apperence lead up to
 * While the earlier villains of Septimus Heap were usually too stupid to be real threats most of the time, Tertius Fume since Queste is the first antagonist that became a threat to the Castle itself, signaling the more serious events of the later books.
 * In Stephen King's IT, while it still had bullies, it is this when IT shows up
 * While opening with a death, Neil Gaiman's Anansi Boys doesn't get truly dark 'til the introduction of Tiger

Live-Action TV

 * In Mighty Morphin Power Rangers, Lord Zedd fits the trope perfectly. In a series known for ineffectual series of monsters and goofball villains, Lord Zedd almost singlehandedly reversed that in his debut by locking Rita Repulsa back in her trash can, restoring Goldar's wings, and causing the destruction of the rangers' old Dinozords. Though the old pattern eventually reasserted itself, Zedd himself was such a serious villain for the show that his character was eventually watered down to avoid scaring the kiddies.
 * Obviously, the fact that Lord Zedd was meant to be a VILLAIN was lost on them.
 * And ironically, it's probably this lasting influence that reduced further villains back to ineffectual or comically inept in subsequent series, horrible as their goals might be.
 * Ineffectual? In the third season of the series, the villains actually had the upper hand for most of the season. So this trope still kicks in.
 * And when Lord Zedd started losing he edge we got the superficially goofy Master Vile... who had MUCH stronger monsters, which would routinely trash the rangers, and force them into a corner while he came closer than ever to ruling the earth. Even his monsters of the week were far more dangerous than Zedd's, having annoying special powers and almost never being defeated in a lame one hit kill zord battle (Despite the rangers having STRONGER zords at this point).
 * What about the guy who actually won? Also, Trakeena from Power Rangers Lost Galaxy actually started out as Daddy's Little Villain and grew into a Knight of Cerebus. Of course, a lot of the events were touched off by Deviot, so maybe he's the real one responsible.
 * Before Trakeena or Deviot, there was the Magna Defender. Not a villain, strictly, but just as bad at first - the series' first Anti-Hero, he was on a Roaring Rampage of Revenge and willing to sacrifice innocents (albeit reluctantly) to do it.
 * Divatox is a weird example. In the movie, she was supremely goofy and whiny, played 100% for laughs, and the evil demon-thing Maligore served this role. In the TV series, at least for the first half of the season, she got a new actress and was a bit more serious. Ironically, when the old actress returned and went right back to being ridiculous, she.
 * Power Rangers Samurai has Serrator, who appears near the beginning of Super Samurai. Not only is he a Complete Monster responsible for, which he admits to face that he enjoyed every minute of, he's leagues beyond the Rangers and routinely beats them down. On top of this, the Nightlock he brings with him are pretty much living torture devices.
 * M*A*S*H inverts this. Its one-shot villains, usually a Colonel or General, often have a high casualty record or disregard for human life. The recurring 'villains' like Burns or Flagg are comically inept.
 * Angelus in Buffy the Vampire Slayer. Not that the show was exactly family friendly up to that point, and plenty of the villains had been genuinely dangerous, but from mid season two (when Angelus turned up) onwards, the show got noticeably darker.
 * The iCarly episode iPsycho, we're inroduced to Nora, an Ax Crazy Fan Girl who trapped the gang in her basement to have them stay at her brithday party. Then we were introduced to her family in iStillPsycho and we saw the most terrifying, adventurous situation Dan ever put the gang in!
 * Scorpius, in Farscape. Within a few episodes he tortures the main character, kills his love interest and usurps the previous villain.
 * Serial killers Mr. Yin and Mr. Yang on Psych. The latter played mind games with Shawn, and later hooked Shawn's mother up to a bomb; and the former, kidnapped Juliet and Abigail, placed them into death traps to taunt Shawn, and got away scot free (for now). A terrified Shawn even remarked during the Yang case that his constant wisecracks were a coping mechanism to keep himself sane.
 * But since he had to focus all his energies on solving the case, he asked Gus to pick up the slack in the goofiness to keep him from cracking under the stress (with hilarious results and lots of awkward looks from everyone else).
 * Supernatural: when Mary Winchester showed up in Season 1's "Home", everything started going downhill. The writers even Lampshade it in the commentary. After they realized how well Jensen and Jared worked together, they made everything more emotional, darker and less comedic...if you ignore "Yellow Fever", "Hollywood Babylon", "A Very Supernatural Christmas", "Mystery Spot", "Monster Movie", "Fallen Idol", "Changing Channels", "The Curious Case of Dean Winchester", "The Real Ghostbusters", " Sam Interrupted" and "Bad Day at Black Rock".
 * Ashes to Ashes has two fairly spooky but ultimately ineffective villains in season one's Clown (who is more a mental/emotional villain for Alex than a true threat) and season two's . That changes in season three, when Jim Keats is brought in.
 * It is pretty hard to pin down the exact point when Castle has started to become darker, but the 3XK certainly fits this trope. Especially since his introductory episode was the series' first one to have a real.
 * Rare for a nonfiction work, but Christopher Childs on Wife Swap certainly qualifies. His family's episode caused things to, rather than be funny Bigot vs. Bigot comedy that's usually the standard, contain little to no laughter but considerably more tear-jerking and/or rage-inducing moments.
 * First, he brainwashes (and admits to purposely doing it) his children into believing his crazy "Christian" lifestyle where women should stay in the kitchen and men rule.
 * Dread sets in when halfway through, it becomes obvious that his replacement wife won't be able to fix his family while Mrs. Childs introduces rules that negatively impact the other family.
 * Christopher's real dark moment is after his replacement wife tells his rebellious daughter Columbia to follow her dreams of becoming a successful woman rather than a housewife. He takes Columbia away in his car (off-camera) and forces the replacement wife to promise to not influence Columbia; when Columbia comes back, she's been brainwashed by Christopher into not only giving up her dreams and becoming a housewife, but also believe that the replacement wife was trying to manipulate her.
 * At the end, it's revealed that neither family learned anything (although the other family was nowhere near as screwed up as the Childs') and have come off worse as a result due to Mrs. Childs' rules being horrible and Columbia being successfully brainwashed.

Theater

 * Camelot is extremely lighthearted up until Mordred arrives, and then starts building toward a genuine tragedy. This could easily have caused Mood Whiplash, but it's handled extremely well.
 * Also in "Into the Woods" when the female giant shows up in act II, lets just say things go down hill from there.

Video Games

 * The Archmage in Grim Grimoire. The moment he stops being mentioned as being a defeated threat and starts being an active character, things get a lot more serious, fast, and what was once a light-hearted magical school drama becomes much darker.
 * Hawke in Advance Wars 2 manages to simultaneously pull off a Knight of Cerebus and a Worthy Opponent. While the game's Quirky Miniboss Squad are about as quirky as you can get without major surgery, Hawke is serious to a fault and Dangerously Genre Savvy, especially when facing off against Eagle: when his giant sea fortress comes under attack by Eagle's squadron is approaching, he says "how predictable" and surrounds it with anti-air units, forcing the player to resort to clever tactics and massive casualties. And later on, he decides to stop Eagle from interfering all together by forcing his troops to march past a place where his air units can't go: an active volcano.
 * Kurtis looked like one of these in the first Disgaea game; up until that point, Laharl's major enemies (Unknown Rival Mid-Boss, Love Freak Flonne, Dirty Coward Madeiras and Lord Error-Prone Captain Gordon, Defender of Earth!) had been little more than comedic interludes, to which the cyborg proved to be remarkably strait-laced by comparison.
 * Malice in Riviera: The Promised Land. Her first appearance is part of a very dark scenario, but the game returns to its lighthearted self when she leaves. Her return marks the shift of the game to its main themes and the serious core of the series.
 * Sunder and Balio in Breath of Fire 3. Up until that point, the game focussed on the light-hearted adventures of Loveable Rogue Rei and his two charges, Teepo and Ryu. After Sunder and Balio torch Rei's treehouse then beat the crap out of and separate the three kids, Ryu begins searching the world for his missing buddies, running afoul of the two villains several more times.
 * The Lego Adaptation Games are a barrel of laughs and fun to play, in Lego Star Wars, the Emperor doesn't abide by this rule, he rarely has any funny scenes to show, minus one with, he's more or less played seriously in comparison to the rest of the games. Lego Harry Potter has an odd aversion of this trope with Voldemort, who ends up more like an Ineffectual Sympathetic Villain.
 * Final Fantasy VI is a generally light blend of mild angst and whimsical humor...up until Kefka usurps the power of the Warring Triad and causes the apocalypse, creating the World of Ruin and becoming a god. The tone of the game completely changes after, focus shifting to the characters trying to rebuild their ranks and find reasons to continue living in a barren and dying world.
 * Kefka is also this to the series in general; with the exception of Cloud of Darkness, all prior villains were generic Tin Tyrants who wanted to take over or destroy the world, and aside from being Evil Overlords none of them got much characterization. Kefka on the other hand quite clearly loved the carnage and destruction he was causing and gleefully Kicked The Dog every chance he got just for the hell of doing it. Since him, the villains of the series have become more sinister and ambitious.
 * , the Big Bad of Pokémon Mystery Dungeon: Explorers of Time/Darkness/Sky. While the earlier villains encountered were either jerks or total idiots at best, this guy, unfortunately, isn't.
 * Even before  appears, the game begins to gradually get darker once   shows up. Ditto for . Hell, even Drowzee can be seen as an example of this.
 * Mortal Kombat 9, as per its series tradition, is normally gory, but things do start out looking good for the heroes despite Raiden's attempt to change the timeline. Then Shao Kahn becomes one by, showing that Raiden's actions started to have disastrous effect. The bad news, that's just the minor one. The next time,
 * Some of the villains from the later Paper Mario series games such as the Shadow Queen and Dimentio.
 * Bowser himself actually became this in the games Super Mario Galaxy and Super Mario Galaxy 2.
 * Dragon Age 2 mostly pits Hawke against ineffective minor villains, Punch Clock Villains, and underdeveloped people who are bad guys because the game tells you they are for most of the first third. And then you meet Sister Petrice, whose fanaticism is downright disturbing.
 * Mega Man Zero was already the darkest series in the franchise to begin with, but when Dr Weil appeared in the third game, the already dark series got Even DARKER!
 * In Amateur Surgeon, everything is (darkly) comedic and quirky until the Big Bad shows up.
 * Every game in the Ace Attorney series has one of these near the end.
 * Ace Attorney: Your rival, while competent, was hardly a monster. The game's first two cases featured villains who were both hammy and incompetent, while the third gave us a morally ambiguous but not entirely evil killer, the fourth case brought legendary prosecutor  Manfred Von Karma. With a super-aggressive courtroom demeanor, demonic voice and appearance, and full willingness to cheat to win, it's a rather jarring turn from the previous case, which concerned a murder on the set of a children's TV show.
 * Justice for All: Hello  The Ace Attorney series will forever be comedic, and it seems to believe very much in well-earned happy endings, but   gave it a definite darker twist that never really left.
 * Trials and Tribulations: An odd case here in  The villainess of three of the games five cases,   is found guilty of murder in the very first one. However, the true depths of her depravity isn't truly revealed until you see what crimes preceded and succeeded that one.
 * Apollo Justice: Like the above example,
 * Investigations: Super-serious and super-dangerous international criminal syndicate leader  who is responsible for just about all of the game's events. While perhaps not as villainous as the other entries, he still takes the cake for his stubborn, utter refusal to admit to his crimes.
 * Investigations 2 has . Unlike the killers of the game's previous three cases, he has absolutely no redeeming features whatsoever, his   streak rivals or even surpasses   (he , for one) and he manages to drives Edgeworth into a Heroic BSOD so bad he   And just when you think it can't possibly get any worse, he crosses the Moral Event Horizon right in front of everyone by   It's no wonder that he pretty much causes   to go: "Screw this, I'm doing a Heel Face Turn."
 * What's most surprising is the final case's killer actually doesn't fit this trope.
 * Shadow the Hedgehog's introduction into the Sonic the Hedgehog franchise took the series down a much darker and grimmer path. Sonic Adventure had a larger share of dark moments than any of the previous games but ultimately contained an upbeat tone. Sonic Adventure 2 (Shadow's debut) is certifiably a point at which the series started experimenting with much heavier themes and Shadow was certainly a catalyst in the series' move in that direction (which continued all the way up to Sonic Unleashed).
 * And he also gets beaten out by Mephiles the Dark in |Sonic the Hedgehog 2006, who was depicted as having no justifications behind his horrific actions other than enjoying destroying things simply because he could, succeeded in murdering one of the heroes, and even successfully shattered the fabric of existence until he was defeated.
 * Reflux in Rayman 3 could be argued as such, having probably the fewest humorous quirks in the game.
 * ZODIAC Virgo from RefleX holds this title for turning what would be a rather regular shmup plot completly on it's head.
 * The Kingdom Hearts series has always been lighthearted even when being grim and morally deep, being a Disney crossover after all. However, the arrival of Master Xehanort in Birth By Sleep made the game the darkest game of the series, . Heck, the Sequel Hook for the game at the end of Kingdom Hearts II serves to show this guy is in a league of his own, showing him freezing Ven solid and raising mountains of earth with a flick of his hand, instantly making him the strongest being the series had seen up to that point.
 * from Pokémon Black and White and Pokémon Black 2 and White 2 versions. With him being an evil mastermind, a exploitative charlatan, a narcissistic sociopath, a megalomaniac Sinister Minister and would be Evil Overlord, a child abuser, a torturer, a terrorist, and an all around evil dickwad who would attempt homicide on a child in order to get his way, the tone is darkened and more serious whenever he's around or even mentioned.
 * Colosseum and XD represents this for the franchise at large, as not only is the Orre region Darker and Edgier than the rest of the known world, the Cipher syndicate is much nastier than anything that came before them and a damn sight nastier than just about anything that has come since. The Sequel Hook after XD does not help, and neither does the implications that . In any of the other games' WMG sections, bringing Cipher up darkens the discussion in record time.
 * As proof, the fanfic Ashes to Ashes pits May and Maxie against Cipher - Maxie already has somewhat sympathetic motives in the source work, so naturally compared to Cipher, he's an absolute saint.
 * Cyrus, boss of Team Galactic in Pokémon Diamond and Pearl, immediately succeeded Cipher as the darkest villain the franchise had seen to that point, being an Omnicidal Maniac with a Messiah Complex who wants to exploit the powers of time/space to tear the entire universe apart and then recreate it into a new reality where every living being is purged of spirit and he reigns over as it's supreme deity. Not a pleasant end goal, and Cyrus' means to this end are no more pleasant.
 * Purple Eyes from Pokémon Ranger Guardian Signs fits this trope to a T.  There's a reason this guy's entry is spoilertastic.
 * In the Kirby series,.
 * Chaos Lord Ledgermayne of Adventure Quest Worlds counts as well. Basically, many villains before it, especially some of the previous Chaos Lords, were lighthearted and comical in nature, and even mainly focused on Incredibly Lame Puns, big deal. Then cue the arrival of Ledgermayne, who proves to be almost invincible due to being immune to regular weapons and magics and even being able to control magic itself. And later, Ledgermayne reveals itself to be a Complete Monster when it reveals its plan to cut off all magic from Lore - all without caring about the fact that all life on Lore will die if it itself succeeds, which it is, of course, fully aware of.
 * Another classic AQ Worlds example of a Complete Monster, Vordred, also proves to be this as well. He shows players that he means business by using his signature spell, the Voiduminance Necrot-Morph, to turn other people, especially the very paladins he was trained to fight and destroy (after all, he is a Paladinslayer), into his undead slaves. And that's not all, his armor, which is made up of Too Many Skulls, is immune to light-based magic, and he gets even more powerful thanks to, plus he's the reason why Part 1 of the Doomwood saga is Darker and Edgier than the previous sagas in the game before it.
 * Bloodtusk Ravine's story proves to be the darkest out of all the Chaos Lord areas so far, seeing how Xing & Xang's scheme for the ravine is darker than their previous schemes were, and not to mention.
 * and, to a far greater extent, in Kid Icarus: Uprising.
 * in No More Heroes. At the game's halfway point of the fifth ranked fight, things have already been getting darker with Travis actually feeling remorse for the last ranked assassin he fought. Then you notice a trail of blood on the street, leading to a long tunnel to the next fight...where someone is constantly just out of your reach. When you actually reach the next fight, . It is at this point where No More Heroes goes from dark comedy to constantly unsettling, with the calls for money becoming more demanding and . The game is quietly telling you and Travis that you have gone down a very dark path, and there's no getting off anymore. There's someone waiting for you at the finish line as well, and you have seen what can do first hand already.
 * The Legend of Zelda Skyward Sword takes a somewhat more balanced approach with the franchise, using dark elements but also lighter moments within the same game, and also lampshading the series' traits, but whenever Ghirahim appears, the game makes a big change in tone, becoming much more serious..
 * Mr. Sandman from Punch Out. This Scary Black Man is the only one of Little Mac's opponents to resemble an actual boxer (opposed to a cartoon-character boxer) as befits one of the hardest opponents in any of the games. He also seems to be the only one who sees his bout with Mac as a personal issue; in Title Bout mode, there is a cutscene showing him training in a gym, then noticing a poster with Little Mac's face, and becoming so enraged at seeing it that he wrecks the entire gym.

Web Animation

 * Zetto in TV Tome Adventures, a Blood Knight who usually shows up in each season around the time things are getting serious.
 * Red vs. Blue introduces, in Reconstruction, several characters who are entirely serious military personnel, including the Director of Project Freelancer (Dr. ), Agent Washington (who isn't actually a villain, but nonetheless marks the shift to a mix of silly and serious for the series) and the Meta, who's a creepy, insane blend of several A.I. It's a considerable shift from Omega's "feast on their bodies and crap out their souls" vibe.
 * double-dips on Knight of Cerebus duty by coming back at the end of the more comedy-oriented series "Recreation" and offing two major characters on the spot.
 * Church, after witnessing  ruthlessly execute fallen enemy   on   advice, summed it up the best: "Dude, you guys are some cold motherfuckers."

Web Comics

 * Damien from El Goonish Shive is a great example of this trope, to the point where
 * Abraham was supposed to be even worse, but the whole thing turned out to be one huge misunderstanding (and even larger idiocy) on his part, so after having everything was explained to him and given a legitimate loophole, he surrendered. He even got to be funny in places, something that did not apply to Damien. Pandora seems primed to do this in-universe, as she seeks to give her son a world where he can make a difference.
 * Order of the Stick has five. In chronological order:
 * Xykon, who has been the Big Bad of the comic so far (but might well be offed before the end of it). His first appearance was in a strip titled "Plot Ahoy," which was the first indication that OotS would be more than a gag-a-day strip about a D&D-style adventuring party. He is unusually humorous for a Knight of Cerebus, in a horrid enough way; how many other villains have a Moral Event Horizon involving a super-bouncy ball?
 * The Linear Guild, evil copies of the main characters. The stakes rose considerably after they appeared, and within a hundred stirps fo their arrival the OotS had destroyed the dungeon in which they had started.
 * Miko Miyazaki is the clearest-cut Knight of Cerebus, a Lawful Good (and overzealous) Knight Templar Hero Antagonist. The author wrote her to see whether he could create a character who could be a recurring antagonist of the heroes while still being Lawful Good. He succeeded a little too well, producing a Broken Base and Internet Backdraft which is still ongoing, several years after . Fans either love her or hate her, but all agree that the comic became much more serious after her first appearance, even though she was frequently a butt of jokes and and had a snarky, dry wit of her own.
 * The Snarl, an Eldritch Abomination formed by the gods' stubbornness in a previous, unsuccessful, attempt to create the world. It has yet to do anything yet in the comic; the forces of good hope to keep it that way.
 * The Inter-Fiend Cooperation Commission, Lee, Nero, and Cedrik. The Linear Guild's employers, trying to get control of the Snarl for themselves. They're extremely powerful and equally competent, even if Cedrik had some wild college days.
 * looked like this, at least to some fans. This may have been an intentional subversion; at any rate, the transformation didn't last long, and was meant as a matter of.
 * Sluggy Freelance kicks its Cerebus Syndrome off with a Mook vampire named Kullan. He fits this trope because his introduction is (a) pretty much the first strip in the series to end on an ominous note rather than a straight-up funny one, and (b) the start of the "Vampires" arc, Sluggy's first more or less serious storyline.
 * As the strip progressed, the presence of Oasis, K'Z'K or HeretiCorp is a fairly good signal that a given arc is going to be darker than usual.
 * Played with in Eight Bit Theater with the Four Fiends. The first two, Lich and Kary are played as fairly serious villains, with their presence resulting in major character deaths (and in the case of Black Belt, Killed Off for Real) and some dramatic moments. The later two, Ur and Muffin subvert this trope, with Ur being killed in an Anticlimax while the Muffin Arc is dealt with humourously as usual.
 * And then we get, which, unlike all other "evils" up to that point, actually causes a major Cerebus Syndrome and manages to kill off half of the cast in less than 10 comic strips before squaring off for THE FINAL BATTLE with the awesomest wizard ever.
 * Satan in CRFH. He even punctuates his arrival by ripping out a main character's soul, just in case we were wondering whether this was a joke.
 * Adventurers! had Eternion, who tried very hard to be a Knight of Cerebus, but only managed to take the webcomic from Gag Series to Affectionate Parody of overblown RPG Saving the World plots.
 * Karnak from Dominic Deegan.
 * The Wanderer, better known as The Cheese, from It's Walky!. Anyone who can be ominous and badass even when people refer him as "The Cheese" is obviously not someone to trifle with.
 * Zebra Girl has always kept a somewhat uneasy balance between funny and dramatic, but it tilted firmly into dramatic territory (and ditched some of its sillier, Fourth Wall-breaking gags) with the appearance of Harold DuVase. This is kind of odd, since DuVase appears at first to be a Harry Potter parody. In the end, he turns out to be something much, much worse...
 * Silas Morth in Exterminatus Now was thought to be one of these... but he really wasn't.
 * Jeff from RPG World is the greatest example of this..
 * Sam and Fuzzy takes a turn for the serious which is arguably kicked off by Fridge. Although he starts off as comic relief, his actions in the "Friday Night" arc drag Sam into the Ninja Mafia plotline that has dominated the last four years of the comic.
 * Last Res0rt was already pretty dark, but by the time we bring Veled around... she's the Big Bad, and she doesn't leave much doubt of it either.
 * Even if she does have more comedic value than most as she's easily bored (and eager for entertainment), Veled never comes off as harmless - in fact, when she's bored, she's even more dangerous.
 * Kore from Goblins, who is introduced by creating a room full of likable new characters, giving them likable personalities in record time, and then sending in the new villain to brutally slaughter the entire bunch. Including an innocent dwarven child. Keep in mind that Kore himself is a dwarf.
 * And a paladin. How he has managed to keep his paladin status is a mystery.
 * Ozimaar from Jayden and Crusader appeared unexpectedly on page 14 after 13 silly comics and created a nonsensical storyline which lasted 'till December '07 when the author cancelled the arc and skipped on ahead in the story, because the Ozimaar Arc was boring him.
 * Then Computer re-appeared rampaging through the ongoing story lines and twisting them onto her self.
 * Despite only appearing once so far, the hooded archer from Slightly Damned counts. Devenol even more so.
 * SSDD has an example of a pre-existing character serving this purpose.
 * Given the ever-escalating nature of Homestuck, there are at least three "candidates" throughout the story so far:  at the end of Act 1 (not a character, but the moment where things start to shift from inventory shenanigans to plot),   in Act 4 and   in Hivebent/Act 5.
 * The Midnight Crew intermission also had one with Snowman. While the Felt were otherwise portrayed as hilariously incompetent gangsters existing only to mess up with their time powers before getting killed by the Midnight Crew, Snowman came in, and spent the rest of her screentime horribly maiming the fan-favourite main characters and generally being what would be a Complete Monster had the Midnight Crew not been Villain Protagonists and the intermission not been Evil Versus Evil.
 * The only somewhat-serious The Dragon Doctors gets a lot more heavy once the Crax chapter begins. It's a horrible flesh-and-mind-devouring parasite, and it's followed up on with a serial killer who kills people with nightmarish death spirits, a Die Hard scenario in a hospital, and tragic backstory after tragic backstory.
 * Although King Nastie came first, the true Knight of Cerebus for The Life of Nob T. Mouse is arguably the Eldritch Abomination known as "Grandfather Time".
 * Kiwi Blitz features the villainess Gear, whose presense is currently the only source of grimness and darkness in an otherwise fun and whimsical webcomic. Until "murder-furries" are discovered... and then they seem to be connected.
 * The chainsaw unicorn from Modest Medusa. It starts a rather bloody fight in what had previously been a lighthearted comic with no action and heralds the start of the Story Arc.
 * Penny and Aggie was just a normal high school Dramedy focusing on the titular characters' lives... up until we meet At first just an ordinary Alpha Bitch, it soon becomes clear  Hell, she's such a Knight of Cerebus
 * Sakana, oddly enough, has a two-person Big Bad Ensemble that function as this, despite their limited appearances.
 * The first half is Ryoji Nishimura, a Smug Snake Perpetual Smiler who wants to use the titular stall for his own shady businesses. That said, his Large Ham qualities tempers his status as this somewhat.
 * The other half is, and unlike Nishimura, there's nothing even remotely funny about this guy.
 * Schlock Mercenary has played with this trope before, but it didn't stick until the introduction of Admiral Emm. Extremely Dangerously Genre Savvy, the only reason the Toughs weren't immediately compressed into neutronium and fed into an annie plant was because Admiral Emm wanted to let Colonel DeHaans torture and mind-rip them first, just to make sure her clean-up job on information was complete and thorough. The Toughs only survived by handing over an expert on  and agreeing to let the UNS mindwipe them. The fact that the very next story arc was the darkest story arc by far didn't help anything. Then things get really gross,, and along comes foreshadowing of the reason why two Tagons either tiptoe or blunder around each other... and then it's shown explicitly in a flashback.

Web Original

 * "Oh, but I am Linkara... More or less."
 * After Mechakara was dealt with, things got sillier again with Dr. Linksano as the main villain... only for a second Knight of Cerebus to emerge: Lord Vyce. "All that he sees, he conquers."
 * The Neanderthals from AH Dot Com the Series.
 * Stalker, the first Complete Monster in Tasakeru.
 * Suburban Knights had the Big Bad, . He scares the living shit out of the regular cast, and with good reason.

Western Animation

 * Both lampshaded and played straight in The Venture Brothers episode "Victor Echo November." When Phantom Limb gets in an argument with Harmless Villain The Monarch, he shows his superiority by calling for the immediate killing of the Venture family, whom the Monarch has ineffectually antagonized for the whole series. When the Guild henchmen prove to be much more dangerous than The Monarch's Mauve Shirts, Dr. Venture asks, "This is different, isn't it, Brock?" Brock replies, "Yeah, we might not win this one."
 * Although by season 4.
 * The Web Creature from ReBoot. The thing itself only appeared in three episodes, all told, but that doesn't matter. The damage had been done.
 * Though he was introduced in the very first episode, Slade from Teen Titans didn't take center stage until the end of the first season, and the previously light and comedic storyline took a much darker turn. Though humor episodes were still very common later on, any time Slade's around things get dead serious very fast. Things get even darker with the introduction of Slade's master, Trigon, though they return to normal after both are defeated. Needless to say, this was a show that tended to dance a jig up and down the Sliding Scale of Seriousness Versus Silliness.
 * Mozenrath from Aladdin. Prior to his introduction, the recurring villains on the show had been a bunch of cartoonish joke characters like Abizz Mal and Mechanikles. Then, suddenly, we meet this highly competent dark wizard with an army of zombies and a magical glove which is slowly eating his flesh. Only his flying eel sidekick prevents him from being too dark.
 * Nox from Wakfu. When most of the villains of the series are harmless, being slightly ridiculous or just not evil at all, Nox is one hell of a dramatic villain. He is eager to destroy any living things to get their primordial energy, including a baby that he stalked for ten years. And some flashbacks seems to indicate that  Altougth it might be a slight subversion, because he was introduced in the very first episode; the later villains were more light-hearted.
 * Apocalypse from X-Men Evolution. After he appeared, the series got less goofy and more serious, with more dramatic tension and more focus on stories about mutant persecution, less on high school drama. Apocalypse's ultimate genocidal plan really emphasized this.
 * Though to be honest, the plot had already become divorced from the High School Drama even before Apocalypse arrived thanks to That was not a very good day.
 * King Hiss in the 2002 He-Man and the Masters of the Universe cartoon. Shortly after being released, he defeats Skeletor and his entire army of evil warriors, before breaking into Castle Grayskull. Although temporarily defeated, he later returns and destroys the royal palace of Eternia.
 * Megatron of Transformers Animated is another semi-example like Slade and Rubilax... Once he gets his body back, things get bad.
 * And then when Shockwave gets involved, things get worse.
 * Chase Young of Xiaolin Showdown was introduced as the Big Bad in the second season. In the first season the villain had been Jack Spicer who was comically beaten once an episode. While he was partly taking orders from Wuya (an evil spirit with no physical form) she was also strictly comical, except in the Season One finale. Chase, hwoever, was a strictly non-comical and threatening villain.
 * Wuya deserves special mention. Like Rubilax, her snarking makes her strictly comedic for the most part... then she gets free and suddenly the laughing stopped.
 * In G.I. Joe: Resolute, Cobra Commander himself has become a darker, edgier, EFFECTIVE villain, explaining away his old incompetence as a (failed) method to coerce his minions into being better soldiers (adaptability, resourcefulness, so on). This CC manages to be a credible threat to the world.
 * For Renegades, he's being developed into a rich blend of Corrupt Corporate Executive, Magnificent Bastard, Complete Monster and Villain with Good Publicity; it's working.
 * In Codename: Kids Next Door, while it has some pretty dangerous villains (like Father and several former allies), they have some Laughably Evil traits while still bringing hard stuff. Then there's Grandfather, a monster of such horrible caliber whose plan is the most evil ever seen in the show, and is the only villain with no funny, sympathetic or redeemable features at all.
 * In The Grim Adventures of Billy and Mandys Halloween Special, there is Jack O' Lanturn. While quite comedic, he is shown to be the only villain to outsmart Mandy by not falling for her trap and capturing her. He is only defeated when Irwin, in the most hillarious use of Deus Ex Machina shows up and humiliates himself enough to destroy Jack's army.
 * In the first Jungle Book film, Shere Khan didn't come in until the final act of the movie. And when he did appear, things took a turn for the darker, particularly where Baloo was concerned.
 * This is somewhat more subtle in the original film, where both he and Kaa are somewhat comical yet legitimately threatening antagonists (even though Shere Khan quickly proves to be the most fearsome of the two face to face). The sequel however plays this Up to Eleven, desposing of most of Shere Khan's whimsical aspects and making Kaa more into an ineffective Butt Monkey.
 * Justified with Shere Khan, since he wants revenge for the humiliation he suffered.
 * His Tale Spin incarnation is similarly far more serious than than in the first film, and compared to the show's other Rogues Gallery is far sinister and dignified (even if there was some humor generated from this). However, in contrast he has a more affable side, his tendancy to side with Baloo on many occasions may prevent him from quite entering this trope.
 * Professor Pericles the parrot from Scooby Doo Mystery Incorporated, who is hands down one of the most frightening villains in the franchise's history.
 * The Freak of Crystal Cove AKA is even worse then Pericles. His deeds involve:   And all this from a villain on a Scooby Doo show.
 * The Lich of Adventure Time is this, as he manages to
 * What really makes him this is he's a Complete Monster and Omnicidal Maniac, all of which are played dead serious. his appearance is pure Nightmare Fuel.
 * While still Played for Laughs for the most part, when Dennis makes his debut in The SpongeBob SquarePants Movie, the movie definitely went downhill from the usually light series.
 * Though already being hauntingly dark, Little Nemo: Adventures In Slumberland, when The Nightmare King shows up, this trope is brought on home.
 * The original Ben 10 series had, for the most part, episodes that feel somewhat like Silver Age stories, with a usually comical feel to it. This rule doesn't apply to Vilgax and Kevin, both having Complete Monster status. Vilgax pointedly showed more explicit hints to the first season's Story Arc and Grandpa Max's Hidden Depths. Kevin demonstrated what the main character, Ben, would be like if he had little in the way of remorse with his powers—although he eventually did a Heel Face Turn and became Ben's Token Evil Teammate.
 * In that same vein, the Forever Knights in Ben 10 Ultimate Alien, combined with Took a Level in Badass. In the earlier series and several earlier episodes, they were pathetic mooks that got beaten easily and usually made Monty Python references. In the episode "the Purge" their founder, Old George returns, ends their Enemy Civil War and unites them as one faction to rid the world of aliens, and the excrement hits the cooling device.
 * Him of The Powerpuff Girls, compared to the rest of the show's Ineffectual Sympathetic Villain cast, had a much creepier presence (even noted frequently by the cast and the narrator) and frequently supplied Mind Rape or other much deadlier tactics of bringing the girls to an end. Granted he also often supplied in Nightmare Retardant and did have the occasional bumbling role (he was Camp Gay after all) but he was still miles deadlier than most of the Rogues Gallery. And then there's the episode "Speed Demon".
 * Dick Hardly from "Knock It Off". Just see why he's Killed Off for Real.
 * Played with in The Dreamstone with Zordrak. While he appears in each episode dishing comical banter to his far less threatening minions, the Urpneys, he is a genuinely intimidating villain, and the odd time he has an active role in a plan it is usually a sign things are going to get a bit more serious.
 * Inverted in My Little Pony: Earlier villains were rather terrifying, while later ones are extremely goofy and hilarious.
 * Also inverted in Season 1 of Friendship is Magic. It began with Nightmare Moon, a Physical Goddess that planned to bring about eternal night (and the apocalypse it entails). After her defeat in Episode 2, the 25% of episodes that weren't antagonist-free Slice of Life featured only minor anti-villains and Monsters of the Week.
 * Season 2 seems to be repeating Season 1's setup by introducing Discord, an Faux Affably Evil villain that brainwashes ponies into being disharmonious For the Evulz. Though in this case, he still plays it straight, as he comes after the season's worth of Slice of Life episodes and Anti-Villain enemies.
 * Still played with since Discord is much more clownish than the earlier Nightmare Moon (both out and in universe apparently) and of about the same threat level. It is interesting to note that several later villains, though lower key, actually have potentially deadly intentions for the cast, while both Discord and Nightmare Moon, though more devastating in execution have amusingly mundane goals (Nightmare Moon wants eternal night while Discord wants to turn Equestria into a Cloudcuckooland).
 * Not that those wouldn't have catastrophic effects: eternal night would usher in essentially a new ice age and kill all plants, and thus, eventually all life on the planet. Discord's brand of chaos would wreak havoc on the world as well, with the laws of physics constantly changing and night and day switching every few minutes.
 * The Canterlot Wedding introduces us to, who plans to.
 * The hunter from Bambi. And to make matters worse, we actually never get to see what he looks like!
 * Word of God says it was Gaston from Beauty and the Beast. (No one orphans deer like Gaston!)
 * Which means that the most advanced firearm that could have possibly shot Bambi's mother was a musket—not the most accurate or long-ranged firearm ever to be invented. If Bambi's mom had been a little more aware...
 * How about Warhok from the Kim Possible Grand Finale? He planned to take Kim to his homeplanet to kill her and mount her on his mate Warmonga's wall.
 * Well, Word of God was that the creators wanted to make the villain as terrifying as Darth Vader.
 * Although Avatar: The Last Airbender was never exactly light or fluffy, considering it launches viewers right into a 100 year war dealing with the consequences of genocide, things get darker when Firelord Ozai is introduced in "The Storm". We discover that in addition to being the leader of the the Fire Nation he also emotionally abused his son Zuko, and burned his face for speaking out of turn. His daughter, Azula, also amped things up in season 2.
 * Amon from the Sequel Series, The Legend of Korra also fits this. The couple of episodes before his first appearance were quite lighthearted. Once he showed up, the series has gotten darker and darker with each episode.
 * Even though he appeared in only one movie, Dark Danny, Danny Phantom's Bad Future version, made quite an impression as the most dangerous and psychotic villain in the entire series, even worse than Vlad Plasmius.
 * Vlad himself served this role in the first season, though to nowhere near as great an extent. His first appearance marked the beginning of the show's main Story Arc, and subsequent episodes that featured him tended to be darker in tone. He was also the first villain to utterly curb-stomp Danny.
 * Darkseid and the armies of Apokolips in Superman the Animated Series. While Superman wasn't a goofy show, being largely a good combination of silliness and seriousness, the eight episodes where Darkseid appears are much more serious that regular episodes. In "Apokolips... Now!! Part 2",  and in "Legacy Parts 1 and 2",
 * Justice League Unlimited had several end of season threats amping up how much darker things were. The last season had this from the beginning via Gorilla Grodd (himself a recurring Knight). What would top this? At the end of that season Darkseid returns and sets out for revenge against the Earth. Not only does he set crust digging machines all over the world to cover the entire surface in boiling magma, he also brings a kryptonite knife to carve out Superman's heart as a war trophy.
 * Professor Screweyes from We're Back! A Dinosaur's Story.
 * Although The Brave Little Toaster is a dark film, it starts getting much darker once the infamous Monster Clown makes his appearance. Alternatively, Elmo St. Peters could be considered a Knight of Cerebus as well.
 * Crud from The New Adventures of Winnie the Pooh; granted, as a stand alone villain, he's a Laughably Evil cartoon blob who wants to make the world messy, in comparison to the rest of the series' Rogues Gallery; howeve,r he's pretty terrifying (especially since most Pooh works don't even have an antagonist). Adding to this is the fact that he's actually voiced by Jim Cummings, using his Robotnik voice!
 * Yosemite Sam of Looney Tunes is another "comparison only" case. At his best he was an Ineffectual Sympathetic Villain Played for Laughs, however he was specifically created to be a far more malicious and active villain for Bugs Bunny than the rather pitiful Elmer Fudd. As Sam eventually became even more harmless than Elmer, Chuck Jones created Marvin the Martian, an Affably Evil alien set on denoting the Earth with an "Earthshattering Kaboom". Even Bugs was pretty creeped out by this.
 * Perhaps the series' oddest move was evolving Daffy Duck into one for Speedy Gonzales. Similar to the above examples, Daffy was still rather bumbling and comical, however he was often portrayed as Speedy's most competent (and malicious) foe compared to the rest of his completely ineffective Rogues Gallery, often putting Speedy and his friends in much more dire circumstances (eg. enslaving them or depriving them of water) and downplaying the former's Comically Invincible Hero streak.
 * Jeff Fecalman in Family Guy. There is absolutely nothing funny about him in the episode he appears in.
 * Stewie Griffin seemed to be this in early seasons, being very competent, until later seasons which have him as more of a gay joke. In this case however, it was more or less completely Played for Laughs.
 * The moment Rattlesnake Jake first appears in Rango, things get really dark.
 * The Drill Sergeant Nasty from "Phineas and Ferb Get Busted". He pretty similar to the Coachman.
 * In The Penguins of Madagascar Dr. Blowhole can be established as one, since he tried to melt the ice in the world, and flood it, so that the humans will have to go through a ring of fire, and in his second appearance he intentionally tried to drown Skipper when he gave him amnesia.
 * Miss Power from Word Girl. Magnitudes more powerful than every other villain and WordGirl herself, and much more intelligent. Pretends to be a hero and trains WordGirl while slowly corrupting her and the citizens. When WordGirl finds out she's being played, Miss Power simply beats her up and takes over anyway.
 * Lord Dregg of the 1987 Teenage Mutant Ninja Turtles cartoon. The fact that he plays his actions more seriously than Krang, the Shredder and his goons, who were all Laughably Evil Harmless Villains, definitely shows that this guy means business.
 * Speaking of the Shredder, he was made EVEN MORE cruel, brutal, and competent in the 2003 cartoon and was even put into Complete Monster territory in said cartoon. Of course, this was just a small change compared to his even more completely monstrous self in.
 * Sykes from Oliver and Company.
 * While the villain of the first Cars film is an arrogant and obnoxious green racecar, the sequel's villains are an organization of evil, beaten-up cars led by a German microcar
 * Sideshow Bob from The Simpsons. In most of his appearences he attempts to kill' Bart ( 10-year old boy'') or Krusty The Clown and his actions are played seriously and episodes become more intense and dark when he appears.
 * Mr. Burns also qualifies, at least in seasons 1-8. While he does have some comical traits and funny quirks, the episodes with him are more serious and dramatic than any other episodes and his actions are played seriously. Most notable examples are "Who Shot Mr. Burns?" two-parter, where he screws over all other characters and finally blocks all the sunlight from Springfield and this was so evil that his loyal doormat Mr. Smithers objects to this and all of his actions are played seriously and episode is dramatic and intense, not to mention that it is the only two-parter episode in the series; The Curse Of Flying Hellfish where he crosses Moral Event Horizon by attempting to drown Bart and in "Mother Simpson" where he worked on biological warfare and made Mona Simpson, Homer's mother, run from the law and hide from the rest of her life, meaning that Mr. Burns is responsible for Homer losing his mother and setting some of the series plots in motion.
 * Fat Tony usually. His overall attitude is much darker and more menacing than most bad guys on the show, and as a mobster, considers very little off-limits. In fact, when he does say something funny, this attitude often makes it seem funnier.
 * The series had few villains who have no funny quirks and are played seriously to the point of going into Complete Monster territory. Examples include the winemakers from "The Crepes Of Wrath", who treated Bart like a slave and nearly killed him by giving him antfreeze-laced wine, the Babysitter Bandit from "Some Enchanted Evening" (who tied up the kids and tried to rob the house) and Bart's kindergarten teacher from "Lisa's Sax" (whose treatment of Bart made him considered suicide, when he was just a five year old boy and made Bart what he is today).
 * Piella. She murders twelve bakers, and plans on making Wallace her thirteenth. This was because she hated bakers.
 * While the show on a whole is much goofier than previous continuities, Ultimate Spider-Man's version of Venom is, half the time, not played for laughs and there are less Imagine Spots whenever he manages to make an appearance.
 * Courage the Cowardly Dog gives us Mad Dog. He abuses Bunny to the point where he buries her up to her neck in dirt when she tried to escape, he tried to drive her and Courage down with his car, and most importantly, he somehow caused Kitty to be convinced that all dogs were evil. And that, like Katz, he's played dead seriously, and that he almost resembles a real life abuser.
 * Katz himself should not be overlooked as well. Whereas the general series dealt with courage battling monsters and whatnot, at least they had some light-hearted tones in those episodes. Katz starkly contrasts these themes as He's essentially Ax Crazy Serial Killer played completely, horrifyingly, and competently straight. Courage usually struggles in the episodes he's in, nearly getting killed twice.
 * Courage the Cowardly Dog gives us Mad Dog. He abuses Bunny to the point where he buries her up to her neck in dirt when she tried to escape, he tried to drive her and Courage down with his car, and most importantly, he somehow caused Kitty to be convinced that all dogs were evil. And that, like Katz, he's played dead seriously, and that he almost resembles a real life abuser.
 * Katz himself should not be overlooked as well. Whereas the general series dealt with courage battling monsters and whatnot, at least they had some light-hearted tones in those episodes. Katz starkly contrasts these themes as He's essentially Ax Crazy Serial Killer played completely, horrifyingly, and competently straight. Courage usually struggles in the episodes he's in, nearly getting killed twice.

Other

 * Makuta from Bionicle started out menacing enough, but his constant defeats and failures gradually robbed him of his credibility. After the original head of the Story Team left, the character of Makuta underwent a serious retcon, which resulted in him turning into a calculating mastermind who had planned his victory from the start, turned out to be the Bigger Bad behind a lot of former villains, and by the end of the story arc, ended up winning.