If You Ever Do Anything to Hurt Her...

""I've never seen my sister this happy, Ian. If you hurt her, I'll kill you and Make It Look Like an Accident.""

- Nick Portokalos, My Big Fat Greek Wedding

The one true manly way to concede defeat for the girl's heart is to tell the winner that, if he ever screws up, he should expect an ass-kicking of epic proportions. Usually uttered by (or sometimes to) The Lancer or The Rival.

This establishes that the loser:
 * Realizes he has lost.
 * Does not give up his role as male protector or lose face for losing
 * Is decent enough to just want the girl to be happy, only expressed in a guy way.
 * Is holding the winner to a very high standard.

The manly and gracious thing for the winner to do is to accept this statement. "I would be disappointed if you didn't." This is not (usually) an insult or a threat, but an agreement between guys who both want the same girl to be happy.

This can also be said by a parent or older brother of the girl, who is relinquishing their previous role as "main male protector."

And yes, an asskicking of epic proportions will follow should any betrayal occur.

Anime and Manga

 * How about a male-warning-gay (well, bi) male example? Hiro, Shuichi's best friend, warns Yuki against making Shuichi cry any more than he already does in Gravitation.
 * This phrase is often repeated by Ryoga in Ranma One Half. Odd thing is that he actually backs up this claim more than once, and often when it just looks like he did something. Also unusual in that Ryoga hasn't really given Akane up yet, nor has he really been beaten.
 * One Piece: Genzo, Nami's father-figure, to Luffy at the end of the Arlong Arc.
 * Apparently, this was supposed to be non-romantic. Not everybody saw it as such.
 * In Shin Chan Georgie gets this warning from Shin, even though Hima is too young for him to be interested.
 * In Adachi Mitsuru's H2, Miyoshi says this to Hiro about Koga. However,
 * Though he'd just apply to anyone, Hitsugaya Toshiro reminded Ichimaru Gin that should he spill one blood from Hinamori Momo, he'll kill him in instant.
 * Medaka Box: Medaka's older brother Maguro tells Zenkichi that he'll keep Medaka away from him if he doesn't have what it takes to protect her..

Comic Books

 * Tag-team variant: in the comic Excalibur, Brian and Kurt (Captain Britain and Nightcrawler) warn teammate Pete Wisdom that if he hurts Kitty (fellow teammate Shadowcat) in any way, they'd rip his head off, desecrate it with graffiti, and drop it in the middle of the English Channel.
 * Wolverine performs the brotherly version in the X-Men comics, after Gambit returns to the team following the blowup about his past misdeeds, warning Gambit that if he hurts Rogue again, he and Logan are going to have some sharp, pointy, adamantium words.
 * An early '80s X-Men comic has Wolverine intending to beat some sense into Colossus after the latter breaks up with Kitty Pryde, but Wolvie settles for getting Colossus involved in a Bar Brawl... with The Juggernaut.
 * He does this again (though a platonic version) with Cable, a former rival, when he realizes that Cable means a lot to Jean, who'd just spent several years raising baby-cable in the distant future. "Far as I'm concerned, the slate's clean between us. Just one thing. If you ever break that girl's heart, I'm gonna finish what I started in Madripoor."
 * In X Men the Animated Series he does it again at Scott and Jean's wedding in more subtle way. He says to Scott that better if he make Jean happy or "I'll find you anywhere.", whlie cutting a piece of wedding cake with his claws.
 * Batman does this to Superman of all people at the end of in the DCAU's 'World's Finest' movie. Bruce Wayne has spent much of the film dating Lois Lane, who calls it off after finding out his secret. Right before he leaves Bruce tells Clark "She's all yours now, if you can handle that. But you'd better be good to her, 'cause I know where you live." The look on Clark/Superman's face is priceless.

Fan Fiction

 * In Lilly Epilogue Family Matters, Mr. Satou, having finally conceded that Hisao is a good match for Lilly, says that he has connections to hunt him down if he does anything to harm her. Hisao wonders if he actually does have those kinds of resources at his disposal.
 * In Earth and Sky, when Big Macintosh notices that Applejack and Apple Bloom are developing attractions to Soarin' and Pipsqueak (respectfully), he takes the latter two aside for a talk, and casually mentions that he doesn't like it when anypony upsets his sisters... and also that he can crush rocks the size of a stallion's head with his bare hooves. Soarin' is suitably scared, but Pip completely misses the point of the conversation.
 * In I Won't Say Light makes it obvious that he has a crush on L but after Mello learns that L feels the same way he takes it upon himself to give Light this warning and he manages to be quite intimidating for a 14-year old kid.

Film
"Gurkin: If you try any funny stuff, I will unleash the power of the internet on you. I will register you as a sex offender in all 50 states... and Canada."
 * The page quote comes from My Big Fat Greek Wedding, but there it's a bit of a subversion. Niko tells Ian he's just kidding... and then threatens him again. Over and over again, including through a cut away.
 * The film Pirates of the Caribbean: The Curse of the Black Pearl has a more subtle example, when Commodore Norrington, after learning that his fiancée really loves the smith Will Turner, tells Will that he expects him "to show the same care and devotion in every aspect of his life" as he does in his work; in the context of the conversation, it is obvious which aspect of Will's life he's particularly referring to.
 * Don't forget that Norrington delivers the admonition while holding his sword inches from Will Turner's face.
 * That's probably one of the best examples of both this trope and of Norrington's character, since Will made the sword in question.
 * In the film Shanghai Knights, after initially objecting to the idea of a relationship between his sister Lin and Roy O'Bannon (Owen Wilson), Chon Wang (Jackie Chan) accepts it, but adds, "Break her heart, I break your legs," to which Owen replies, "That's fair."
 * Boba Fett steals this line in the Star Wars Expanded Universe while another Mandalorian informs him that he is going to marry Fett's granddaughter.
 * At the start of The Godfather, Connie Corleone (Talia Shire), sister of Sonny Corleone (James Caan), marries Carlo Rizzi (Gianni Russo). When Sonny finds out that Carlo has hit Connie, a rather lengthy beating takes place. (This was so severe that Caan actually broke two of Russo's ribs and chipped his elbow.)
 * It's mentioned in the book that Sonny's threat "If you touch my sister again I'll kill you!" makes everyone relax, as he'd never say that if he was willing to kill Carlo (because it could be used as evidence against him). Mind you, Sonny isn't exactly cool-headed over these things, which his enemies use to their advantage.
 * In the film Sydney White, the protagonist scores a date with the current Big Man On Campus, Tyler Prince. Tyler is informed by the seven nerdy boys who share their house with Sydney that there will be severe punishment for any funny business. Of course, being nerds, this is their definition of severe punishment:

"Hal: "You deserve her ..." [uncomfortably] "... more than me. But lemme tell you something, if you ever mess up and make her unhappy, I'll be waitin' in the wings. And I'll pounce on you. Like a ... tiger! Like a tiger on a deer! With a cloven hoof, with a broken ... arm!""
 * Although, frankly, that's a very effective threat.
 * In Clueless: Hey, you. Anything happens to my daughter, I got a .45 and a shovel. I doubt anybody would miss you.
 * In Shallow Hal, when Hal thinks that Rosemary and Ralph are back together, Hal comes to Ralph to concede victory:

"Sam: You listen to me! You listen good and proper. Anything happens to him, you'll have me to answer to. One sniff that something's not right, one hair that stands up on the back of my neck, it's over. No more slinker, no more stinker. You're gone. Got it? I'm watching you."
 * In the film Something New, Kenya and Brian embark on a double date with Kenya's friend and her fiance. When the ladies excuse themselves to go dancing, the other guy tells Brian that while he likes him and he seems to be an "okay guy", he thinks of Kenya as a sister and even if not, she's his girlfriend's best friend, so Brian had better not be using Kenya as some "science experiment" (Brian is white and Kenya is black).
 * Towards the end of the "Real Thing" sequence from Big The Musical, Susan's "oldest, longest, dearest" male friends casually warn Josh, "Don't hurt Susan, or we'll break your kneecaps if you do."
 * Bad Boys II has one of the absolute best versions of this trope when Marcus and Mike terrorize Marcus' daughter's date. It has to be seen to be believed.
 * In the extended cut of The Lord Of The Rings: The Return Of The King. Samwise Gamgee gives Gollum a warning about betrayal and harming Frodo when the latter becomes suspicious of what lies in Shelob's Cave.


 * Dom make his intentions clear to Brian should he hurt Mia in any way: "You break her heart, I'll break your neck."

Light Novel

 * The Student Council President gives this to Layfon in regards to his sister Felli in Koukaku no Regios. It's played entirely for laughs, since Layfon has no idea that Felli likes him, and the President is wearing a Badass Longcoat over a red and white striped bathing suit.

Literature
"Jace:Is this the part where you tell me if I ever do anything to hurt her, you'll kill me?
 * The Redemption of Althalus sees
 * Sibyl's brother to Dorian in The Picture of Dorian Gray
 * An unusual example in Wolf of the Plains: Temujin threatens the father of his wife-to-be with massacre of his entire clan if he beats Borte again. Note that Temujin grows up to become Genghis Khan.
 * Subverted in the Mortal Instruments trilogy, when Jace prepares himself for this speech from Simon, his girlfriend Clary's protective best friend. Of course, Clary is a demon-slaying Shadowhunter.

Simon:No. If you hurt Clary, she's quite capable of killing you herself. Possibly with a variety of weapons."

"Ygritte: A man can own a woman, or he can own a knife, but not both."
 * Sadrao says this to Trent in Black Dogs, which is quite justified as Trent is the son of the book's Big Bad, and Sadrao is worried that the whole thing might just be some kind of dark scheme.
 * In A Song of Ice and Fire, Jon Snow and Tormund Giantsbane are discussing the latter's new son-in-law. Tormund threatens him by saying that he'd rip the boy's manhood off and beat him with it if he broke his girl's heart. However, the wildlings of this story kidnap women to make their wives as a standard practice, with the acknowledgment that the woman ultimately chooses whether to stay.

Live Action Television
"Wesley: I just don't want to see her hurt.
 * Uttered by Wesley to Gunn on Angel:

Gunn: What are you, man, her brother?

Wesley: Apparently..."

"Gunn: And to add the necessary boilerplate, you ever hurt her, I'm gonna kill ya like a chicken.
 * And later in reverse:

Wesley: Acceptable terms."

"Michael: If you harm a hair on Stanley's head, I will burn Utica to the ground."
 * Subverted in Friends: Ross tells Chandler before his wedding to Monica that if he hurt her, he would "hunt him down, and kick his ass"... to Chandler's great amusement and laughter. Which is interesting, considering that, in a later episode, the others find it laughable that Chandler could beat Ross up.
 * Of course, then in another episode Ross and Chandler are stuck in an arm wrestling match due to being "equally weak". For the joke is that neither of those guys is remotely violent or physically threatening. Phoebe on the other hand...
 * Part of the point was that if Chandler screws up, Monica can and will kick his ass before Ross even manages to punch Chandler hard once. Though there is that whole "My Sandwich" incident...
 * But it's played very straight in the wedding episode--when Chandler disappears for a second time (although this time he WASN'T making a run for it), Ross flat-out tells him he won't let him run out on Monica.
 * Eight Simple Rules for dating my daughter: #6."I have no doubt you are a popular fellow, with many opportunities to date other girls This is fine with me as long as it is okay with my daughter. Otherwise, once you have gone out with my little girl, you will continue to date no-one but her until she is finished with you. If you make her cry, I will make you cry."
 * Another good one is # 4: "I'm sure you've been told in today's world, sex, without using a 'barrier method' of some kind, can kill you... let me elaborate; when it comes to sex, I am the barrier, and I will kill you."
 * A non-romantic version occurs in an episode of Scrubs: J.D's feckless and goofy older brother, acknowledging that his brother will never look up to him but admires Dr. Cox intensely, warns Cox in perfect seriousness to take his responsibility as J.D's mentor more seriously, "or you'll have me to answer to."
 * When Elliot is following Dr Cox's bad advice on getting Jake's interest ("First you engage him, then you ignore him"), the Janitor swoops down on a bewlidered Jake to demand "What did you say to make Eliot run off like that? Because it you hurt her..." The Janitor would later kidnap Keith to make the same point.
 * Used in The Office, (US Version) in "Phyllis gets Married", where Michael Scott says to Bob Vance, Vance Refrigeration: "If you ever lay a finger on Phyllis, I'll kill you." Bob Vance replies with, "If you ever lay a finger on Phyllis, I'll kill you."
 * In another episode, Michael goes to prank the Utica branch after learning that Stanley wants to transfer.

"President Josiah Bartlet: Just remember these two things: she's nineteen years old, and the 82nd Airborne works for me."
 * Since parental threats are allowed, we can't forget (president) Jed Bartlet's on The West Wing:

"Lewis: (to Drew) If you hurt my sister, they will never find any piece of you. Not even your glasses. Remember: I'm a janitor. I know how to dispose of things."
 * And he likes Charlie!
 * Queer As Folk features one (gay) man warning his (idealistic) close friend's new love interest: "If you break his heart, I will break your face. Now if you'll excuse me, they're playing my song."
 * Noahs Arc: Ricky says this verbatim to Wade regarding Noah (and means every word of it).
 * In The Mentalist episode "Bloodshot", Rigsby delivers this warning to Grace's new boyfriend, who takes it gracefully and assures Rigsby he'll treat her well.
 * The Drew Carey Show:

"Sam: Anything happens to Sookie, I promise... I'll be sharpening a stake with your name on it."
 * That 70s Show has Eric threaten Casey Kelso with "If you make her cry, I'm coming right back here to kick your ass". Which, considering who is involved, is quite the threat.
 * An episode of Bones when Hodgins was about to marry Angela had Angela's father warning Jack: "I've got caaars and I've got guitaaars. And I've got guns. Treat my little girl right, and you'll only see the business end of the caaaaars and the guitaaaaaaars."
 * Inverted with Booth telling Bones' brother that if he broke her heart again, he would hurt him. And knowing Booth, he would and could carry out that promise.
 * Angela's father does follow through on his promise, although without guns he just strands the guy in a desert and gives him a permanent tattoo of Angela. This is even after Angela tells him that they both called off the wedding.
 * Star Trek the Next Generation. When Vash says she wants to go off and see the universe with Q, Picard makes him guarantee her safety in payment for saving Q's life in an earlier episode (Well even Picard could hardly threaten an omnipotent being).
 * In ER, during Abby and Luka's wedding, Lucien, who is rather fond of Abby, goes up to Luka and warns him if he ever hurt Abby, he would kill him. Which Luka, who was busy trying to find Abby and knows that Lucien is quite drunk, absently gave him an "all right".
 * In the Doctor Who episode "Flesh and Stone", the Doctor threatens the soldiers that if anything happens to Amy while he's away, "I will hold each of you personally responsible. Twice."
 * Occurs in the True Blood season one episode "Cold Ground" when Sam confronts Bill.

"If you do anything to hurt her, I shall personally have you torn to pieces by wild dogs."
 * In Chuck, after Morgan starts openly dating Casey's daughter, Casey grudgingly lets the relationship continue, but warns Morgan that if he breaks her heart, Casey will "break [his] everything." Surprisingly, this does not happen more often, even from such people as Sarah's father or her ex (probably because Bryce knows Chuck is a good man).
 * On American Dreams when Meg's first date shows up her older brother J.J calls out to their little brother to "go clean the shotgun"
 * In The Fresh Prince of Bel Air, Uncle Phil (of course), Will, and even nerdy Carlton have displayed this attitude towards nearly all of Ashley's dates.
 * Beverly Hills 90210. Dylan warns Brenda's fiance Stuart about this. Rather hypocritical considering that Dylan himself broke Brenda's heart.
 * In Psych Lassiter has a truly epic moment delivering one of these. At first unwilling to accept that Juliet was dating Shawn, he eventually closed himself and Shawn in a small room, hooked himself up to a polygraph and then said that if Shawn screwed up he would shoot him. Cut to the polygraph needle showing that he is telling the truth.
 * In Downton Abbey,  marry his daughter, but warns:

Music
"Brother, here's some brotherly advice
 * The Rodney Atkins song "Come on in Boy" seems to avert this at first, as the girl's father merely tells her date how much his daughter means to him and that "she deserves the best." However the last line in the chorus the father promises he'll see them when they get back, as he'll be up "still cleaning this gun."
 * The basis for the song "Welcome to the Family" by Little Big Town is a man detailing to his new brother-in-law how scary his family is.

If you know what's good for you'll treat her right

'Cause Grandpa's the local sherriff, yeah, he's the judge and the jury too

Uncle Bill's the undertaker, son he'll dig a hole for you

Cousin Jesse, he's just crazy, he'll fight you just for fun

Mama's got a real bad temper, and Daddy's got a shotgun"


 * Tom F. Wilson in his Daughter Song.
 * A musical implied variant (sort of "Male Reassuring Female"), the song "Separate Ways (Worlds Apart)" by Journey includes the lines "If he ever hurts you / True love won't desert you".

Stand Up Comedy
"If you touch her, or hurt her, or make her sad, I'm going to hurt you twice as bad."
 * Christopher Titus during his "LOVE IS EVOL" special mentions telling his new younger girlfriend's father that he'd take care of her. Her father, a Vietnam Veteran Marine Pilot, basically tells him, if he doesn't, "One Shot, One Kill".
 * Later he jokes about how his body would be found over four states and he says that her brother, a federal agent, says, "They ain't gonna find ya."

""Boy? Look at me. See that girl over there? She's my only daughter, man. She's my life. And if you have any ideas about trying huggin' or kissin'... you remember these words. I got absolutely NO problem going back to prison.""
 * Bill Engvall's segment of the Blue Collar Comedy Tour, to a boy who has come to take out his daughter:

Theatre

 * The whole point of "She's My Sister" in the musical Memphis. The show is set in 1950s America, and in this particular song Delray, an African-American club owner, warns Caucasian Radio DJ Huey Calhoun just how much danger he's putting his little sister in by being involved with her in a time when interracial relationships were illegal.

Video Games
"Guybrush: If you did anything to hurt Elaine while I was gone, I swear I'll--
 * In Mass Effect 2, after re-recruiting Tali, you'll get an email from the quarian Admiralty Board saying (in somewhat formal diplomat-speak) "She's with you now. You're her captain, so what you say goes. Don't screw up or you'll have the whole fleet on your ass." Only at the end of the email does it say that the message is from Tali's father specifically. Bonus points since Tali is one of male!Shepard's possible Love Interests.
 * To anyone not familiar with the game (shame on you), the Quarians have the largest fleet in the galaxy.
 * Becomes Harsher in Hindsight
 * In one of the flashbacks in Assassin's Creed Brotherhood, Ezio gives one of these to Manfredo, the man who his lover Christina became engaged to while he was off in Tuscany hunting the Pazzis.
 * Discussed and parodied with Guybrush and a human LeChuck in Tales of Monkey Island Chapter 2: The Siege of Spinner Cay:

LeChuck: The only thing I did to Elaine was to pull her from the freezing water along with a bunch of wet, screaming monkeys!

Guybrush: [smiles] Actually, that kinda sounds like our honeymoon!"

"Fenris: You're living with Hawke now?
 * In Dragon Age II, if Hawke romanced Fenris, then romanced Anders, you get this banter.

Anders: What's it to you?

Fenris: Be good to him/her. Break his/her heart, and I'll kill you."

Web Comic
"Rayne: It goes without saying that should you cause her to so much as frown slightly - (evil face) The revolutionary guard will find you on the Iranian border, wrapped in an American Flag and in possession of a camera filled with pictures of their nuclear reactors."
 * From Least I Could Do when Rayne realises

"Gil: I do not intend to have Agatha escape one prison by entering another. She will not be used as a political pawn. She will not be enslaved "For the good of the empire". You knew me at school, and perhaps didn't take me very seriously. That would be a mistake. You must understand this. When I come to her, she will be safe, unharmed and free. Because I will come to her. And if she is not, I will destroy "Her Undying Majesty", melt what is left of your miserable island to slag and boil the seas around it for the next thousand years! Do you understand?
 * Sir Kehydius to Sir Tristram in this Arthur King of Time and Space strip.
 * In The Phoenix Requiem, Robyn does it to Jonas in this strip.
 * In the webcomic Archipelago, shortly after declaring his love to Alice, Riley meets her five brothers. They are not impressed, especially since Riley is half-wereshark, a race almost universally hated. Alice manages to reconcile them, but the eldest pintur still gives Riley this touching farewell speech.
 * An epic variation appears in Girl Genius, with Gil threatening a political rival instead of a romantic rival:

Wooster: You...you couldn't!

Gil: Couldn't?! Couldn't?! I am Gilgamesh Wulfenbach, little man! There is nothing I couldn't do, had I cause! (quiets down) And now, now I have one. Do. You. Understand?

Wooster: Yes, Ohgod yes! Yes, Master!"


 * The Mega Crossover fancomic Girls Next Door gave us one where Erik warns Raoul ... which gets subverted quickly because the effect is not the same over Skype, Erik being the Murder Is the Best Solution type and Christine standing right behind him.

Web Original

 * Although there's no spoken dialogue, it's probably safe to infer that this happens in some form in There She Is, from Il-ho to Nabi. Even without the words there, the emotional context is definitely present. He carries through with the threat part in Step 4,

Western Animation
"Danny: *nervous* Uh...hi, you must be Paulina's father. *gulps as her father cracks his knuckles*
 * Spoofed in Futurama, when Zapp Brannigan tells Fry (who is pretending to be Leela's boyfriend) that if he screws up or hurts Leela in any way, Zapp will dive in to take his place "...like a fly on a particularly seductive piece of manure."
 * Kim Possible:When Kim Possible and Ron Stoppable start dating (thanks to some encouragement from the Moodulator), Kim's dad warns him that he'd better not make Kim unhappy unless he wants a one-way trip to a black hole.
 * Similarly in Danny Phantom where Paulina's father declares to her date, Danny...these lines...

Paulina's Dad: If you upset her...We're going to have a very violent talk.

Then a few minutes later.

Paulina's Dad: I know where you live.

Danny: *leaves with Paulina* And I'm glad we had this chance to chat!"


 * Scooby-Doo and Ghoul School have the fathers of the monster girls warning Shaggy and Scooby what they'll do if the girls are unhappy. The fathers consist of pretty much all of the classic Universal Horror monsters.
 * Let me tell you something. You lay ONE PAW ON MY DAUGHTER AND YOU'LL BECOME MY PERSONAL TOOTHPICK YOU HEAR ME!

Real Life

 * A Real Life example, President Barack Obama once noted that his pre-teen daughters were fans of Boy Band the Jonas Brothers, but added "Boys, don't get any ideas. I have two words for you: Predator drones. You will never see it coming. You think I'm joking." Of course he was joking--it was a White House Correspondents' Association dinner, so joking is traditional--but as the Senator from Minnesota might put it, perhaps the First Dad was "kidding on the square" a little bit there.

Anime and Manga

 * In Death Note, the Shinigami Rem who seems to be female threatens to kill Light if his schemes do anything to hurt Misa.
 * Light being Light, he manipulates Rem into carrying this threat out on someone else. Just as planned.
 * Tokyo Babylon:
 * In Kimagure Orange Road, Madoka often warns Kyosuke to not make his sort-of girlfriend Hikaru cry. Problem is, Kyousuke cares for Hikaru yet is in love with Madoka... and Madoka also falls for him, despite her efforts to aid Hikaru and her own reluctance to admit it. In the anime, it didn't end well. This also applies to the local Chew Toy, Yuusaku, who loves Hikaru despite her rejecting him often and constantly warns Kyosuke to not hurt either her or Madoka.
 * Indirectly delivered in Cardcaptor Sakura; after confessing her love to Yukito and being turned down, Sakura wishes him luck with her older brother Touya, and tells Yukito that if Touya ever hurts him, she'll beat him up for Yukito.
 * Shortly after Takayuki and Haruka hook up in the first episode of Rumbling Hearts, Haruka's best friend Mitsuki warns him not to string Haruka along, or she'll make him regret it...violently, if necessary.

Comic Book

 * Queen and Country has a scene where Tara delivers this warning to her mother's fiancé, in French.

Fan Work
"Misa: Hello, Mr. Great Detective! Play nice with Raito-kun; he's a genius but a bit difficult. Oh, and if anything happens to Raito while he is under L's care, Misa-Misa will destroy him if it is the last thing she does!"
 * In the Death Note AU Ragnarok Misa warns L:

"Misha: "I TOLD YOU TO TAKE CARE OF SHIICHAN! IF YOU'RE CHEATING ON HER OR MAKING HER CRY, I'M GOING TO FLY DOWN THERE AND KICK YOU IN THE BUTT SO HARD YOU WON'T BE ABLE TO SIT RIGHT FOR A MONTH!""
 * In Weekend At Hisaos, Hisao gets into an argument with his girlfriend Shizune. After they get back to his house, Shizune texts her best friend Misha,, and she angrily calls Hisao, demanding to know what happened and delivering this warning.

Film
"Sister-in-Law: If you screw this up I'll fucking kill you.
 * Happens in a short and funny scene in Jerry Maguire when Jerry has "The Talk" with his new sister-in-law. After multiple characters have warned him about the talk, Jerry braces himself, goes in, and has "The Talk", which consists of:

Jerry: ... I'm glad we had this talk..."

Literature

 * In the Dragaera novel Yendi, Vlad gets that warning from his wife's erstwhile assassin partner. Lampshaded in that he sees it coming and tries to head it off (but gets it anyway).
 * Mayrie, Tayend's sister, warns Dannyl from The Black Magician Trilogy in this way, before they've even become a couple.

Live Action Television
"Willow: Have fun! And remember, if you hurt her, I'll beat you to death with a shovel.
 * The pilot episode of Dharma and Greg: Dharma's friend, upon meeting Greg for the first time, warns him that "she'll bring him pain he can't even imagine" if he hurts Dharma.
 * From Buffy the Vampire Slayer:

Riley: [pulls questioning face]

Willow: [matter-of-fact-ly] A vague disclaimer is nobody's friend."

"Dawn: Spike. You sleep, right? You. Vampires. You sleep.
 * She didn't, though.
 * From "Beneath You":

Spike: Yeah. What's your point, niblet?

Dawn: Well, I can't take you in a fight or anything, even with a chip in your head. But you do sleep. If you hurt my sister at all... touch her... you're gonna wake up on fire."


 * Drake from Drake and Josh had to deal with this from his Sadist Teacher Mrs. Hayfer as he was dating her daughter, threatening that "If you break her heart, I'll break you." Though getting sick of his date's bad laughing habit, he struggles throughout the whole episode figuring out a way to break up with her without invoking Mrs. Hayfer's wrath.
 * In ER, Carol Hathaway's mother is not happy upon hearing that her daughter is engaged to Doug Ross, as he treated her horribly during their first relationship (cheating on her frequently). As Carol walks away, her mother declares, "He will regret the day he was BORN if he hurts you again."
 * Good Luck Charlie has one when Teddy tells her parents that she's dating her ex boyfriend Spencer again--who she broke up with because he cheated on her. Teddy's mom gives her blessing and then says "If you ever hurt my little girl again... BAM!!"

Video Game
"Isabela: I get the feeling that girl's messing in something big and dangerous. Look out for her, will you? Make sure she doesn't hurt herself. Oh, and if you do anything nasty to her, I'll cut off your balls."
 * In the third Jak and Daxter game, after Tess gives a new BFG to Jak, and tells him that she wants him to protect "her little baby" (Daxter) with it, or else she'll "hunt him down and hurt him REAL BAD."
 * Isabela will give this warning to a Hawke romancing Merrill.


 * She'll give a similar warning to a female Hawke as well.

Visual Novel

 * Tokimeki Memorial Drama Series 1 : Nijiiro no Seishun : Minori Akiho gives this speech to ["Heroic Mime|the main protagonist / Naoto when she gives her blessings for his relationship with her dear senpai Saki Nijino in the game's Best Ending."]

Web Comic
""If something happens to her, whether or not it was your fault, I'll come back and kill you.""
 * Zeetha to Gil in Girl Genius. Complicated further by the fact that he's still not sure she doesn't need hurting.
 * Though not made to a romantic rival, this epic threat by Gilgamesh is similar in spirit.
 * Sarine Elle of Errant Story delivered such a speech to former Ambassador Rarune regarding his own half-elf daughter.


 * Featured in Queen of Wands, with an unusually detailed threat.
 * Wapsi Square has the older sister doing the standard issue, but turns around and yells at the younger sister that her date arrived and to get her ass downstairs.
 * In Shadowgirls, when Charon threatens Jerk Jock who was trying to rape her daughter she uses this trope in interesting way by assuring him that she will do terrible things to him if anything happens to Becka, including accidents.
 * In Leftover Soup, Jamie gets a double dose of this.
 * In Sinfest Baby Blue tells Crimney she is sparing him for Fuschia's sake, and if he ever hurts her, she will destroy him.

Western Animation
"Mai: I think it means I actually kind of like you. [kiss] But don't ever. Break up with me. Again."
 * Avatar: The Last Airbender has a frankly scary (non-romantic... most likely) warning from Zounds!
 * Happens to Zuko again in the series finale... from his love interest, at that!

Fan Work

 * In DC Nation, Victor Stone gave this speech to Aurora when she started dating Gar. After Aurora shared a mind with Gar's batshit ex (Terra), she concluded that Vic was understating the warning.

Film

 * The movie Clerks, when the otherwise childish and adolescent Randal Graves seriously warns "Oh, hey Caitlin. Break his heart again this time, and I'll kill ya. Nothing personal."

Live Action Television
"House: (smiling) You're a cold-hearted bitch who ripped his heart out. I watched him struggle for years to overcome the damage you did, and there's no way I'm just gonna let you reel him back in so you can do it all over again."
 * Spaced: Mike, who is intensely jealous of Tim's new girlfriend Sophie, warns her that "You hurt him, I'll kill you." Sophie, shocked, asks Tim if he was serious... to which Tim chuckles good-naturedly and replies, with complete, genial sincerity, "Yep."
 * House: Wilson warns both Cameron and Stacey not to get House's hopes up only to hurt him later (he's a lot nicer about it with Cameron).
 * In the episode "Knight Fall," we get House threatening a girl for Wilson. It's sort of a variation, though, as he's threatening Wilson's ex-wife, who is rekindling a relationship with Wilson, and so it's more like "You've Already Hurt Him And I'm Not Going To Let You Do It Again."


 * On Due South, Ray Vecchio gives this warning to Frasier's Femme Fatale girlfriend. It doesn't help.

Web Comic

 * Ratheel of Juathuur warns Veithel.

Anime and Manga

 * Vision of Escaflowne has Merle, Van's Catgirl Unlucky Childhood Friend, deliver this to Hitomi after she decides that she'll stop trying to fight fate over Van's obvious crush on Hitomi.
 * The Tower of Druaga has an inversion of sorts. After Kaaya's and Neeba's betrayal, Fatina, who previously had a crush on Neeba, gets over him and shifts her affections to Neeba's half-brother Jil. Unfortunately for her, Jil never gets over Kaaya. After the two make up, Fatina slaps Kaaya as a punishment for previously breaking Jil's heart.
 * In Puella Magi Madoka Magica, a non-romantic variety occurs; when Sayaka

Fan Work

 * Equestria Chronicles has Fireflare, who both gets warned and gives the warning on seperate occasions.
 * In the Mega Crossover fancomic Roommates it's delivered by Mrs. Norrington (mother of Commodore Norrington) to . Here.

Film
"Max: If you break her heart, I will hunt you down and kill you.
 * Watts to Amanda Jones in Some Kind of Wonderful: "You break his heart, I break your face."
 * DEBS (2004). Just before Amy and Lucy run off together, Amy's partner Max gives Lucy a warning.

Lucy: [smiles] Deal."

"Victoria: So if you break his heart, I will kill you. And bury your body in the woods."
 * Red has Victoria warning Sara, while looking through her sniper rifle's scope.


 * Subverted somewhat in that Victoria has no interest in Frank romantically; she's just speaking as a friend.

Literature

 * In Meg Cabot's Missing series, Jess warns her brother's girlfriend "if you break his heart, I'll break your face." When her other brother begins dating her best friend, she repeats the same warning to her brother.

Live Action Television

 * In Chuck, Sarah, who has feelings for Chuck, gives essentially this threat to his new girlfriend.
 * Lynnette to in Desperate Housewives.
 * In The Fresh Prince of Bel Air, Hillary warns Jazz's fiance about this.

Music
"And I'm gonna protect you till I die
 * The song "Seven" by Vagiant has a variation where a girl warns her ex that she will beat up any girl who hurts him (which isn't really a fair warning, but whatever).

I won't let nobody hurt you again

I'll fuck up your next girlfriend if she breaks your heart"

Web Comic

 * This Arthur, King of Time and Space strip.
 * This Questionable Content strip.
 * Invoked shortly afterward (in-universe) when Faye chews out Dora . Faye admits that she screwed up, but that there would also be hell to pay if Dora screwed up and hurt Marten]].
 * None of which bodes well for Dora currently

Western Animation

 * Once on Ben 10, Gwen chews out Ben's crush Kai for insulting him: "He's a person, not a pet! You can't talk to my cousin like that! Only I can talk to my cousin like that!" Entirely non-romantic in context.
 * Seems more like unfortunate timing with that particular phrase, as it's a long-standing schoolyard "older sibling protects younger sibling" line.
 * Danny Phantom: Sam does this to  in the episode "Lucky in Love."