Your Worst Nightmare
A common way for a character to announce him/herself in an intimidating manner. It doesn't matter whether he's a good guy or a bad guy, as long as the character is badass enough to live up to this claim. That is, unless people are spoofing this line (often by the second character describing his actual worst nightmare).
Your Worst Nightmare
Anime and Manga The Dragon Ball Z dub seemed to enjoy characters using this trope. And having its "victims" point out how unintimidating they sounded. The Tree of Might Ocean Group TV Edit DubPiccolo: I think you'd better let the boy go. Turles: Oh? Is that right? And just who are you? Piccolo: I'm your worst nightmare. Turles: I'm trembling in my boots.
Goku vs Burter and JeiceBurter: Hi! I'm your worst nightmare! Burter! Goku: I'm not afraid of dreams.
The final sentence of Goku's I AM speech after he became a Super Sayian to Frieza in the Funimation Dub has this gem.Goku: Ally to good, nightmare to you!
Transformers: Cybertron:Undermine: Identify yourselves! Megatron: I am Megatron. Starscream: And I'm your worst nightmare!
In episode 14a of Tamagotchi, as he is about to deal with a gang of thieves, Mametchinosuke the samurai introduces himself with "I'm your worst nightmare - Mametchinosuke, the master swordsman of Gotchi Castle".
Comic Books Batman often uses this phrase when a criminal asks what he is.
Superman in Action Comics (New 52): "Rats. Rats with money. And rats with guns. I'm your worst nightmare."
The Sandman (1989)'s Merv Pumpkinhead: "Lady, I'm your worst nightmare. A pumpkin with a gun." Justified, as Merv is a literal nightmare. Which is based on the infamous subplot from Steve Gerber's run on The Defenders: "I'm your worst nightmare. An elf with a gun!"
Used as a joke in a Frank and Ernest strip where Ernest is being chased by a giant sausage that says: "I'm your WURST nightmare!"
Green Lantern (Kyle Rayner) to a group of alien invaders in JLA (1997): "I'm your worst nightmare. A Manga nut with a power ring!"
Grushko from Global Frequency introduces himself:Grushko: Did you ever have a nightmare about a large man who killed your parents, and your siblings, and then your lover, and then everyone you know? And then burned down your house and destroyed everything precious you've ever conceived of? That was me.
Mysterio uses this during a robbery in the 2019 Symbiote Spider-Man series.Woman: You're me taking a test I didn't study for. And I'm naked? [Beat Panel] Mysterio: Just open the damned vault.
Literature Discworld: Guards! Guards! has: "Someone out there was going to find out that their worst nightmare was a maddened Librarian. With a badge."
Spoofed in Hogfather. Teatime uses this line on a guard, but his would-be victim wants to know which nightmare that would be. When it's clarified that he means, "The one where the man appears out of nowhere and kills you stone dead", the guard relaxes and points out that that nightmare isn't particularly scary. Then Teatime kills him stone dead.
In Snuff, Vimes makes Stinky the goblin a Special Constable, and Stinky responds to Vimes' quip that someone's worst nightmare is "a goblin with a badge" with "Stinky don't need no badges, fellow po-leess-maan! Stinky worst nightmare all by himself!"
Sidorio from Vampirates describes himself as the sort of thing your worst nightmares "wake up screaming about."
In Dean Koontz's Watchers, one of the characters is Vince, an insane hitman who believes he absorbs the souls of the people he kills. Near the end of the book he meets Travis, a Shell-Shocked Veteran of Delta Force:Vince: I'm your worst nightmare! Travis: Not even close.
Live-Action TV Burn Notice: Simon is called a "walking nightmare" by several characters as well as the on-screen character designation captions.
Doctor Who: In "The Girl in the Fireplace", the Doctor isn't saying this to the monster, but well within its earshot, while fighting it:The Doctor: Even monsters from under the bed have nightmares. Reinette: What do monsters have nightmares about? The Doctor: Me!
Spoofed in "Mummy on the Orient Express". The Doctor needs to investigate the Monster of the Week, so walks up to The Captain brandishing his psychic paper, an all-purpose ID which makes him appear to be someone important to whomever it's shown to.The Doctor: I'm not a passenger. I'm your worst nightmare. Captain Quell: [looks at psychic paper, looks disgusted] A mystery shopper. Oh, great! The Doctor: Really? That's your worst... Okay, I'm a mystery shopper.
"The Witch's Familiar" has a variant when Doctor steals the chair of Davros, creator of the Daleks, and then rolls up to the Daleks in it.The Doctor: Admit it! You've all had this exact nightmare.
Family Matters: When Steve's pen-pal in France reveals herself to be evil, her boyfriend introduces himself as Steve's worst nightmare. Steve replies that his worst nightmare is having a ton of cheese and no mouth to eat it.
Used for comical effect in an episode of Herman's Head where Louise (Yeardley Smith, better known as the voice of Lisa Simpson) says it to a tyrannical boss two heads taller than her.
In the 90s miniseries based on Stephen King's IT, Pennywise says to the Losers' Club, "I'm every nightmare you've ever had! I'm your worst dream come true! I'm everything you ever were afraid of!"
In the L.A. Law episode "Spanky and the Art Gang", Gwen Taylor finally meets the woman who's been stalking her:Gwen: Who are you? Woman: Bad dream. Your worst nightmare.
In the Mystery Science Theater 3000 episode "Teenage Caveman" the bots have a squirrel say this to the title character when he has rather more trouble catching than he should.
Power Rangers: The Titanium Ranger's introduction in Power Rangers Lightspeed Rescue
In the Mighty Morphin' Power Rangers episode "White Light: Part 2", Kimberly delivers a variation to tiny!Rita as the Rangers re-seal her.Rita: Oh no, not you again! Tommy: Afraid so, Rita. Kimberly: We're like, you're worst nightmare.
Uttered verbatim by Riker while showing off his poker skills in Star Trek: The Next Generation.Geordi: I do not BELIEVE it! Riker: I'm your worst nightmare.
Tales from the Crypt: One story has a woman tangling with three CIA agents. She has killed two of them (not bad for a housewife) and faces the last agent, woman to woman. The housewife tells the agent, "I'm your worst nightmare. I'm a woman with balls!" The agents acts dismissive about it. The housewife ends up revealing that s/he's the male rogue CIA agent they're looking for. S/he easily kills off the agent! She clearly wasn't kidding when she said that!
In a promo for ABC's upcoming revival of Press Your Luck, a Whammy appears and calls himself the game shows' worst nightmare.
Broad City: Abbi says this to a man in "Coat Check" after she has to threaten him to get him to give her Kelly Ripa's coat.
Music Emilie Autumn's "Gothic Lolita":"I am your sugar, I am your cream, I am your anti-American dream "I am your sugar, I am your cream, I am your worst nightmare, now scream!"
Fall Out Boy's "Novocaine": "Singing I am your worst, I am your worst nightmare"
Video Games One of Anders' battle cries in Dragon Age II.
In Dragon Age: Inquisition, this boast is repeatedly made by the Nightmare. It's Not Hyperbole; he is literally a demon of fear, and does indeed take the form of what scares you most (spiders, in the Inquisitor's case). This is in addition to verbally taunting you with your greatest fears, doubts, and guilts.
Cyan from Final Fantasy VI says this to the captain of the troops attacking his castle, and then defeats him in about two/three turns. "I am Cyan, retainer to the king of Doma. I am your worst nightmare..."
Lo Wang in Shadow Warrior (1997), is everybody's worst nightmare, at least according to himself.
"Welcome to the castle of nightmares! I'm your greatest nightmare!" So says the Tsukiko Johjima, Final Boss of Castle of Shikigami 3.
Soul Series: "I will show you the greatest nightmare!"
Bruce Irvin's only opening pose in Tekken.
In Dynasty Warriors 8, We have Li Dian, who is the most awkward member of Wei. He makes impromptu Freudian Slip Love Confessions (regardless of the Player Character's sex) as his praise quote if he's an allied officer and the player is performing well. and introduces himself with "I am Li Dian, your worst nightmare!" if you encounter him as an enemy (and you are not playing as Yue Jin).
Downplayed in Undertale. The final boss of the neutral route, Photoshop Flowey, is accompanied by a track entitled "Your Best Nightmare". Considering exactly what Photoshop Flowey looks like, it's justified. It also ties in with Flowey's normal theme, "Your Best Friend".
In Mortal Kombat 11, Rambo introduces himself in his introduction trailer with the line back in Rambo III, against water-manipulator Rain and man-eating Mileena.Mileena: Who're you?Rambo: I'm your worst nightmare.
Sven T. Uncommon says this upon confronting the titular heroine of Popful Mail.