Deadly Hug

Melvin: Now, who wants a hug?
Tristan: I do!
Yami: Tristan, no! He's just going to stab you or something!

Melvin: Don't listen to him, Tristan. He just wants all the hugs to himself.

—Yu-Gi-Oh the Abridged Series

Bob and Alice meet in secret for a night of passion. Bob draws Alice close, kisses her deeply and...BLAM!

Alice slumps down dead, with Bob holding up a previously hidden pistol. She's just gotten a Deadly Hug. A sudden gunshot is the most common, but a stab is not unheard of.

When a bad guy does this, it's usually during The Reveal that they're evil. When a good guy does it it tends to be a Mercy Kill. A horror variant has the hugger turn into a monster in mid-hug and crush the victim.

Subtrope of Died in Your Arms Tonight. If the killer had some genuine affection for the victim, this may segue into Cradling Your Kill and/or Pietà Plagiarism. May be the result of a Cooldown Hug gone wrong.

As a Death Trope, Spoilers ahead may be unmarked. Beware.

Examples of Deadly Hug include:

Anime and Manga

In Scrapped Princess, this is how Prince Forsythe kills his twin sister, Pacifica, shortly after meeting her for the first time in his life. When they embrace, he draws his sword and stabs her in the back. Then kills himself, along with her, out of remorse; which sets the End of the World Special in motion. They get better.
Bleach: Hinamori hugs Aizen, who had faked his death earlier, talking about how much she missed and admired him. His response is that admiration is the furthest thing from understanding, and he stabs her through the chest.
Done to Keiichi in the Watanagashi-hen and Meakashi-hen arcs of Higurashi no Naku Koro ni
- Also done in the ending of the Onisarashi-hen manga arc by Natsumi to Akira. Akira doesn't die, though.
At the end of Jin-Roh: The Wolf Brigade Fuse shoots Kei as she cries into his chest (she knew it was going to happen though).
In Gun X Sword, the Claw kills a disobedient minion this way. First he cracks some bones with the strength of the hug and then he impales the guy through his back. It's not clear whether this was deliberate or accidental.
Attempted in Episode 4 of Darker than Black. Mai's father hugged Mai in what seems to be a Crowning Moment of Heartwarming, only to reveal that Mai's father was going to stab his daughter to stop his daughter from becoming a Contractor. Subverted when Mai's father is killed by a Contractor assassin before he can kill his daughter, which leads to his daughter sacrificing her emotions to kill the person who hired the assassin.
In Soul Eater this is how Tsubaki kills her (evil) brother. Although it's approaching it from the other direction; until that point she was unwilling to attack him (even though he was more than willing to kill her and eat her soul to copy her alternative forms for himself) and it's more of a hug while she's attacking him than a bluff of any sort. This shows him that she really cared about him and wasn't pitying him when they were kids (It Makes Sense in Context) and he dies, allowing her to take his soul and gain his powers.
How Sasori died.
In one of the last episodes of Revolutionary Girl Utena Anthy appears to hug Utena from behind before stabbing her through with a sword.
Innocent Venus has one combined with The Reveal, though it didn't actually kill Jo.
How the Black King killed the Red King in the backstory of Accel World.

Comic Books

Pictured above, the end of Bruce Timm's story "Two of a Kind" from the first volume of Batman: Black and White.
Sin City does this a couple of times. Dwight does it to villain Ava at the end of A Dame to Kill For and a nameless hitman does it in one of the short stories to a woman who apparently put the hit out on herself.
In Marvel Comics, the Soviet Super Soldier Ursa Major is a man who transforms into a bear - his bearhug can be deadly.

Film

Blade stakes his vampire mother this way.
This is also how Freddy kills Nancy in Nightmare on Elm Street 3, while impersonating her deceased father. She tearfully embraces him and says her goodbyes...only to have him gut her, much to the horror of her friends and the audience who felt certain she'd survive since she was the main character!
Neff kills Phyllis like this in Double Indemnity.
This is how Commodus kills his father in Gladiator.
How Wolverine finished off Phoenix in X-Men: The Last Stand.
- Kid Omega kills Dr. Rao by hugging her and then extending his spikes.
In the mostly forgotten David Cronenberg film Rabid, the girl has a spike that allows her to feed on her victim's blood in her armpit. She therefore kills by hugging them.
In All the Boys Love Mandy Lane, Mandy and Chloe reunite so they can flee to safety together and Chloe is in hysterics. They embrace; Mandy soothes her and thrusts a hunting knife into her.

Literature

In one very strange short story^[context?], a man has rescued his little daughter from the cult her seemingly crazy mother had taken her to. The mother calls him that night, begging him to bring her back, he doesn't know what she is, and they're the only ones who can contain her. The man scoffs at this, but then takes a closer look at the ball his daughter's been playing with. Just as he realizes it's a puppy's head, his daughter hugs him from behind. Tighter..and tighter.
King Imre stabs Cathan Macrorie in the back in Camber Of Culdi. Imre promises reconciliation after their disagreements (including over the fifty human hostages), and the embrace to seal the deal is the moment Imre chooses to act.

Live-Action TV

Buffy does this to Angel in the season 2 finale of Buffy the Vampire Slayer, although she has to let go of him first since she does it with a sword.
In Angel, Gunn does this to his vampirized sister.
Done in the Doctor Who episode "The Pandorica Opens" by an unwilling Manchurian Agent replicant of Rory to Amy, who refuses to flee despite his increasingly desperate warnings.
Victor does this to Sierra, then collapses and is shot by rioters so they can escape the attic in the Dollhouse episode "The Attic".
An unusual heroic example occurs in the Psych season 5 finale when Yang embraces Yin,while both attempted this,Yang reacted first and impaled Yin with a syringe.
Battlestar Galactica. After finding out their daughter is alive on a Cylon basestar, Helo does this to his Cylon wife Sharon, shooting her after she pleads that her death and resurrection is the only way to get on board the vessel. The shock effect is because the audience comes in in the middle of the conversation, so we don't realise what it's about until the gunshot.
The X-Files ("Leonard Betts"). The eponymous character gives one to his partner after she starts freaking out on finding he's still alive (hardly surprising, as the last time she saw Betts his head had been ripped off). While hugging he injects her with a lethal dose of potassium chloride to keep his secret.
Oz. When prison guard-turned murderer Clayton Hughes takes over the solitary wing and declares himself "President of Huru", Warden Glynn (who regards Hughes as a surrogate son) goes in alone to try and talk him down. Hughes promises to give himself up if Glenn hugs him "like you did when I was a child". Glenn does so and nearly gets stabbed in the back by Hughes, his life only being saved by an inmate seeking the Warden's favour. Clayton however gets fatally stabbed by his own blade during the struggle.

Tabletop Games

In the Dungeons and Dragons book Greyhawk Adventures, a non-player character is described as the last she smiled was when she enticed a man into a hug and stabbed him in the back in order to rob him.
Call of Cthulhu (tabletop game) campaign Masks of Nyarlathotep. The Cthulhu Mythos leader M'Weru likes to embrace her victim and cast the Hands of Colubra spell. When the spell changes her hands into the heads of poisonous snakes, she uses them to bite her victim and poison them.

Videogames

In Battle Chess this occurs when a King or Queen captures the opposing piece. In the case of a checkmate delivered by the Queen, she stabs him in the back with a concealed dagger. In the case of a King capturing the Queen, she tries the same stab but is knocked down by the King with his scepter before she can pull it off.
Mass Effect 2 shows dying assassin Thane killing Nassana Dantius this way, hugging her right after dispatching her bodyguards and shooting her in the stomach, cradling her gently as she expired a few seconds later and laying her down on her desk.

Webcomics

In Drowtales, Jer'kol attempts to smother Ariel with a hug but is stopped by Vaelia.
- Earlier, when Mel hugs Ariel, Ariel thinks this is what will happen, because she has been told Mel is Axe Crazy. However, Mel may be a Crazy Cat Lady, but her affection for Ariel is entirely genuine.
In The Chapel Chronicles, Chapel and Rupert are crying in panel two because Buffy just stabbed Angel.

Web Original

The turn-into-a-monster variant (often accompanied by a Bedmate Reveal) is popular in Creepypasta.
In Yu-Gi-Oh the Abridged Series, Melvin is very fond of doing this; often with a chainsaw.

Western Animation

The Simpsons: Sideshow Bob brainwashes Bart into killing Krusty by hugging him, which will complete a circuit and make them both blow up.
This is how Conway Stern betrays Archer, stabbing him in the back during a manly hug.

Real Life

Boa constrictors and pythons.
- And bears.
The brazilian's expression abraço de tamanduá (anteater's hug, which means to betray someone's trust), refers to the very strong arms and sharp claws of anteaters. Their hug is deadly to anything that tries to attack them.