A bad guy cruises along for a few episodes, or sometimes a few seasons, and isn't really taken seriously. Maybe a huge war is on and you know the good guys are going to win, because of Contractual Immortality. Suddenly a main character or a fan favorite brutally dies. This shows that this threat is Dead Serious.
This can be done either to get the audience off on the "right" foot with a new villain, or to beef up a previously unimpressive one. It can also be used after a Face–Heel Turn to spur the villain's former comrades into finally acting against him instead of trying to get him back on their side. Such moments also might be used for a Tonight, Someone Dies rating stunt.
This trope is basically The Worf Effect pushed to its logical conclusion, a subset of Anyone Can Die, and/or one of the effects of Knight of Cerebus. If the character who is killed has a name and a well-developed background, he's a Sacrificial Lion. If he has a name, but his background is fuzzy to non-existent, he's a Sacrificial Lamb. If the dead guy has no name and no background, he's just a Red Shirt.
As a Death Trope, all Spoilers will be unmarked ahead. Beware.
- Hughes' death at the hands of Envy in Fullmetal Alchemist, made more tragic because Hughes was a Family Man and one of the most notable comic relief characters in the series. His death was also a turning point in the shaping of the resolve of various characters.
- In Digimon Adventure 02, when Myotismon returns as MaloMyotismon, the writers do a great job of making you really, really wanna see the bastard get what's coming to him by having him brutally slaughter his two lovable minions. Sad that after that, he proves to be all talk.
- Digimon Tamers has Beelzebumon, who after his debut spends some time cruising around and slaying a few powerful monsters in the wild before properly confronting the Tamers and killing Leomon, which traumatizes the kids and introduces a grim Tone Shift just in time for the Genre Shift to Cosmic Horror.
- Krillin's death (the first time it happens!) in Dragon Ball is an example of this. It showed that Piccolo Daimou was no joke and marked the first death of a main character.
- One Piece fans all figured that Ace would be rescued, since 'no one ever dies in One Piece, except in flashbacks' is a common mantra among the fandom. They were wrong, and shortly afterward, Whitebeard also died.
- In Tengen Toppa Gurren Lagann, Kamina spends all his time rampaging around the landscape with his brother Simon and the Dai-Gurren Brigade before they decide to take a ridiculously huge mobile battleship as their base by stealing it. Owing to Simon freaking out over seeing a kiss between his crush Yoko Littner and Kamina, his big bro punches some sense into him; opening him up to a fatal strike from Thymilph. He's still so badass that he gets back up and avenges himself, pulling off the series' first Giga Drill Breaker, but dies immediately afterward. Cue Simon's Heroic BSoD.
- The first sign of how utterly dark a Magical Girl series we're dealing with in Puella Magi Madoka Magica comes in the climax of the third episode, where Mami gets Eaten Alive by Charlotte, the episode's Witch of the Week. Though Charlotte herself is killed almost immediately afterwards, the Witches as a whole go from Monster Of The Week to genuinely terrifying threat, as it has been established that anyone can fall victim to them.
- Bleach had never killed a named character among the good guys - of course if we're talking about the manga, and not filler/movie material. Then, in the last arc of the manga (announced by the chapter title "Final Arc - The Thousand-Year Blood War"), after the enemies just showed up, they killed Sasakibe Chojiro, vice-captain of the 1st Division. Well, his name is actually the only thing we really knew about him, but during his funeral, it was established that he was actually a much stronger warrior than he apeared to be, and thus the new enemies are to be taken very seriously.
- Gets played with much more severity when the current Big Bad successfully kills Captain-Commander Yamamoto. After the reader finally gets to see the terrifying things Yamamoto can do with his Bankai.
- Re:CREATORS: Despite its focus on action and drama, the series was still willing to treat the idea of fictional characters coming to the real world with some degree of levity. Mamika's death in episode 8 swiftly puts an end to that.
- Vreveil from Sands of Destruction is always regarded as a credible threat, but really shows just how dangerous he is when he revokes Kyrie's powers and kills Morte for daring to interfere.
- In the season 1 finale of Sailor Moon, the DD Girls subvert being a Quirky Miniboss Squad by successfully killing off Sailor Jupiter. The remaining Sailor soldiers are taken out in various battles with the DD Girls (successfully evening the numbers mind you) — all to make it more poignant that Usagi face Queen Beryl alone in the second part.
- DC Comics have been using this trope repeatedly in their Crisis Crossover storylines. The best example might be Dr. Light, who suffered from Villain Decay to the point that he was a joke among The DCU, and returned to true villainy in Identity Crisis.
- The Superman franchise presents several examples:
- Mister Mxyzptlk was generally regarded as an unimaginably powerful but mostly harmless nuisance... until Whatever Happened to the Man of Tomorrow?, in which he decides to destroy the Man of Steel's life. By the end of the story, he has caused the deaths of Jimmy Olsen, Lana Lang, Pete Ross, Krypto, Bizarro... and very nearly kills Superman off, forcing him to break his vow and kill Mxyzptlk because there was no other way to stop him.
- Similarly, Toyman was somewhat of an idiot who used mechanical toys to antagonize Superman... until a 1990s storyline (later retconned) in which he murders Cat Grant's son.
- Post-Crisis Reactron was easily overpowered by Supergirl in his first appearance. Several months later, he got himself a Deadly Upgrade, murdered Supergirl's father, spent most of New Krypton arc hounding her, and was ultimate responsible for the demise of the Kryptonian race.
- Wonder Woman (1942): Di's early villains were considerably less threatening than they would later become due to the fact that any time anyone actually died they'd just get tossed on a slab in Paula's laboratory and brought right back to life. Then Dr. Psycho escaped from prison and blew up Lila Brown, one of the very few recurring characters, and basically obliterated everything above the knees making it clear that even Di's friends and allies could be killed off for real and establishing Dr. Psycho as a legitimate threat.
- Invoked in Superman story "Hanging the Drapes" when Mister Mxyzptlk, after spending decades bugging the Supers with stupid pranks, decides to challenge them to stop him from destroy Earth. A character complains he was supposed to be just an annoying prankster.
Trickster. Prankster. More a nuisance than anything else. Nothing Superman had said before he took off for space had prepared her for this; the earlier stories were at least by comparison innocent.
Make Earth like Krypton.
That was no prank.
This wasn't funny!
- Jaune Arc, Lord of Hunger: Qrow dies a few chapters before the Final Battle is to take place, showing that Anyone Can Die and establishing that the heroes are no longer being protected by Plot Armor.
- An in-universe version in The Mountain and the Wolf: The Wolf is viewed as dangerous in combat but his repeated claims of trying to conquer Westeros for the Chaos gods aren't taken seriously (the man himself states that he doesn't know why it hasn't happened yet and is waiting for the gods to send him another vision so he knows what to do). After King's Landing is taken, the Wolf tries to steal the Iron Throne, is caught by Daenerys, and she's killed in the ensuing battle, and the Wolf is believed to have drowned. Then some time later he reappears, and the Chaos Gods are confirmed as a real threat by priests of R'hllor.
- Scar from The Lion King may be scheming to usurp the throne by offing his brother Mufasa and nephew Simba, but he doesn't seem that impressive when his best minions are some comically inept hyenas. Then, to illustrate that he is indeed a serious threat, he murders his brother by throwing him into a herd of stampeding wildebeest to be trampled to death.
- Wash was killed off in Serenity purely so that the audience would spend the rest of the battle freaking out every time a character was injured. And earlier in the same movie, Book's death, along with the destruction of every single safe haven the crew's ever had is the main impetus for the crew to actually deal with the Operative.
- Animal House: Most of the antagonists of the film spend the climactic parade riot in various states of Heroic BSoD, except for Sociopathic Soldier Neidermeyer, who after a few moments yelling to his fellow ROTC members to man up and fight, grabs one of the rifles the squad brought along, loads it with live ammunition that he was carrying in a pocket for some reason, and starts looking for someone to shoot. If not for a Deus ex Machina, Flounder would have been the only Delta to get killed.
- Harry Potter:
- Cedric Diggory's death in the fourth book is to show that Cerebus Syndrome is really about to set in as Voldemort is restored.
- Sirius Black's death at the end of the fifth comes right before Harry is told about his destiny, and that no one can protect him.
- Snape kills Dumbledore at the end of the penultimate book, showing that Anyone Can Die in the finale.
- The Star Wars Expanded Universe novels:
- Gandalf and Boromir in The Lord of the Rings, facilitating the Genre Shift of the story.
- Dr Heightmeyer in Stargate Atlantis.
- From Buffy the Vampire Slayer:
- Up until Jenny Calendar's death in "Passion", the Scoobies had been more concerned with restoring Angel's soul than actually stopping him, but killing her off apparently crossed a line that let everyone know he was serious. Joss Whedon confirms that that was the point he wanted to make. No one is safe as of this episode, and Angel is not "just a little evil," he's not "grouchy," he's truly evil and Buffy has to do something about it.
- In Season 6, Warren initially seems like a Harmless Villain, and is dismissed by Buffy as a "pain in my ass"... until "Dead Things", where he uses a Mind-Control Device to brainwash his ex-girlfriend Katrina Silber, nearly rapes her before it wears off, and then kills her to prevent her from escaping. The icing on the cake is when he uses magic and time-distorting demons to convince Buffy she had accidentally killed Katrina, though Buffy realizes the truth just before she turns herself in. From here on out, Buffy realizes how dangerous Warren really is and swears to bring him to justice.
- Also when Jonathan died in "Conversations With Dead People".
- Chuck is a mostly light-hearted, tongue-in-cheek show about spies. Following his Face–Heel Turn, Daniel Shaw cements himself as the show's Knight of Cerebus the moment he guns down Orion aka Stephen Bartowski in cold-blood. From then on, he's the one villain in the show never played for laughs.
- Edward Kerr wanted out of his contract for SeaQuest DSV season 3. The powers that be forced him to stick around for the first few episodes so as to unexpectedly kill him off midseason, underlining the show's Darker and Edgier Retool.
- You wouldn't call the first season of Supernatural cheery, exactly, but the death of John Winchester in season two is what marks the show's sharp descent into complete misery for all major characters.
- In season 2 of Justified Dickie Bennett does not appear to be much of a serious threat compared to his mother Mags or his older brother Doyle. His attempt at a solo criminal career is easily thwarted by Boyd Crowder. Then he kills Aunt Helen and thus causes all the bloodshed that ends the season.
- An alien terrorist proves his seriousness by killing engineering crew member Lt. Joseph Carey on Star Trek: Voyager.
- The Walking Dead: New Big Bad Negan makes his debut at the end of season 6 brutally murdering Glenn and Abraham. This serves as a reality check for Rick, as he'd grown a bit of an ego after taking out the Claimers, Terminus, and the Wolves with minimal losses, and initially did not view Negan as a serious threat.
- Older Than Steam: Romeo and Juliet: Though neither side is presented as inherently more evil than the others, the death of the formally comical Mercutio as a result of the Capulet/Montague feud lets everyone know things are about to go straight to hell.
- In Macbeth the murder of Lady Macduff, her son and the rest of the family marks the point where it's clear there's no coming back for Macbeth himself; his wife kills herself with guilt shortly after, and this act urges Macduff to join Malcolm in the resistance - and be the one to stop him.
- Protagonists start dying left and right in late Act 5 Act 2 in Homestuck. Interestingly, there are no fewer than 6 killers and most of them end up dying themselves or are protagonists forced to Shoot the Dog.
Hussiebot: Oh god, you're right! There are still a few characters I haven't killed yet. I almost forgot about them.
- The first few times qualify, but afterwards, what with the various dreamselves, alternate timeline clones, dreambubble dwellers and what not, Killed Off for Real gets kind of hard to define. Plus, since the number of characters who haven't been killed at least once by now can be counted on one hand, it's questionable whether or not deaths are truly serious anymore.
- Reka's death in RPG World.
- The Head Alien of It's Walky! proves himself a true threat instead of a comedic one when he captures all abductees and starts executing them, one by one.
- Intentionally invoked in morphE the sweet and charismatic villain has had time to earn the favor and forgiveness of most of the cast and many of the readers. In chapter 4 he reminds us that he is quick to kill for petty reasons by executing main character Billy Thatcher for attempting to harm one of his portraits. This reason it is intentionally invoked is that Amical used magic to move back in time a few seconds to shoot Billy in the shoulder instead. The killing was purely for the audience to see that he would kill them and wonder if he has done this to anyone else at any other time.
- In G.I. Joe: Resolute, Cobra Commander sets out to prove to the world that he is no longer a cowardly idiot he has Storm Shadow kill Bazooka and he blows up Moscow. He also kills Major Bludd in front of his troops to show he's not taking anymore crap from them.
- In Invincible Omni-Man kills the original Guardians of the Globe in the end of the first episode of Invincible. Before Omni-man killed the them all, the series is first thought to be a light hearted super hero show before its tone is truly established by the end of the first episode.
- Airachnid's sudden and brutal murder of Breakdown in Transformers: Prime serves to illustrate that this homicidal, Axe-Crazy villainess was no longer content just standing around the bridge of the Nemesis and taking orders.