[Abu Bakaar and Tony Stark shake hands]
Tony Stark: No, he won't.
Yinsen: No, he won't.
Two characters, who are usually active antagonists to each other, make some sort of bargain. Both of them independently decide to break it. Often this is a sign of Genre Savvy on the part of everyone concerned.
A common result of the Scarpia Ultimatum. A classic instance of this is Prisoner's Dilemma, where each party would gain if they're the betrayer, but lose if they're the betrayed. Also compare Hostage for MacGuffin, a more specific situation where the heroes wait for the villain to betray them before doing likewise.
One common result, especially in more comic situations, is for one character to guilt-trip the other over the betrayal, before revealing their own cheating.
It's All About Me characters will regard their own cheating as beneath mention, but rage about the treachery of the other character.
The name is a pun on the game-theoretic notion of "Nash equilibrium", which in certain settings leads to this kind of behavior. See these pages on The Other Wiki for more details.
- In Vinland Saga, Viking mercenary Askeladd makes a deal with a Frankish lord to assist the lord in capturing a fortified town in return for half the spoils. As soon as the battle has turned in their favor, the Frankish lord plots to double cross and betray Askeladd and keep everything... only to learn that Askeladd and his men (who managed to enter the town before the lord's men did), have already taken all the loose treasure and have jumped in their boats and are sailing down the river, having anticipated the lord's betrayal and acted first. Askeladd shouts from his boat that the Franks can keep the town and credit for the victory as their "half" of the treasure.
- Superman vs. Muhammad Ali: An alien race called the Scrubb challenges Earth to Combat by Champion. After defeating Superman in a boxing match (Superman was depowered by red sunlight), Muhammad Ali becomes Earth's champion and faces the Scrubb champion Hun'Ya in a boxing match. After Ali wins, the Scrubb ruler angrily orders Earth invaded anyway, only for a recovered Superman to reveal he anticipated their treachery and sabotaged the Scrubb's space armada.
- In A New Hope, Leia lies to Tarkin about the location of the rebel base and then discovers he was going to blow up Alderaan anyway, even if she told it to him. Tarkin then has the nerve to be affronted that she lied and furiously orders her executed in a fit of pique.
- This is par for the course in the Pirates of the Caribbean movies, especially the third one.
- In Pat Garrett and Billy the Kid, Billy and a deputized ex-crook get into a Ten Paces and Turn kind of duel. When they start taking steps, Billy immediately turns, draws his gun, and waits. When the deputy tries to turn and shoot a couple of steps before reaching ten, Billy's ready for him.
- Chrysalis (RinoZ): Anthony makes a deal with the queen of Liria, to help her reclaim her throne, then steals the payment before the job is done, anticipating that she won't keep faith with a monster. Sure enough, as soon as she has what she wants, she declares, "You can only blame yourself for trusting too easily, creature!" and summons her guards. While running away with the loot, Anthony internally admits that it would have been pretty embarrassing if she had actually kept to the deal since he caused massive property damage preparing his escape tunnel — but it was plain from her manner and tone that that wasn't going to happen.
- The Silmarillion, immediately after the death of Fëanor:
"Then Maedhros ... persuaded his brothers to feign to treat with Morgoth, and to meet his emissaries at the place appointed; but the Noldor had as little thought of faith as had he. Wherefore each embassy came with greater force than was agreed; but Morgoth sent the more, and there were Balrogs."
- The novelization of the strategy game Warhammer: Mark of Chaos had this going on with its Chaos protagonist. It's made clear from the beginning that he and his superior loathe each other since the latter is a sorcerer and he is a Khornate Champion, meaning he abhors most magic. When they get to the resting place of the MacGuffin, the sorcerer decides he doesn't need his champion anymore and turns around to incinerate him, only to notice and narrowly evade the axe headed for his head. The following fight ends after the initially losing Champion receives a gift of his god making him near-immune against all magic.
- This happens in the Discworld novel Mort. Death and Mort agree to begin their fight on the count of three. Both of them attack on two.
- In the Percy Jackson and the Olympians series Zeus, Poseidon and Hades — the Big Trio of gods exhibiting sibling rivalry of divine proportions — make an oath not to have any more children with mortal women, since said children become too powerful and could be used against each other. As even gods cannot be expected to keep it in their pants for too long, Zeus and Poseidon both break the oath and father children. (Hades had fathered children before they made the oath, and he hides them in a Place Beyond Time to protect them from the other two.) When the children or 'demigods' are found, it escalates the rivalry from divine proportions to... something even more divine.
- The game show Golden Balls uses this trope in a Prisoner's Dilemma-type scenario. The two remaining contestants have a set amount of money which they have won and they can either share or steal the money. If they both share they get equal amounts, if one shares and the other steals then the one that stole will get all the money, if they both steal then they both lose the money. Of course a lot of the time both people steal after having a five-minute discussion with the other contestant about how they're not greedy and they want them both to have money.note
- In Lost season 3, Ben agrees to send Jack home in return for Jack surgically removing his spinal tumor. Once in the operating room, Jack uses his momentary advantage to facilitate Kate and Sawyer's escape, risking Ben's life. Later, Ben reveals he never had any intention of letting Jack leave the island.
- In season 3 of The Wire, Stringer Bell and Avon Barksdale, who've been partners since the beginning of the series, end up simultaneously betraying each other. Stringer gives Avon up to the police; Avon arranges for Stringer to be killed. Both continue to swear that they're brothers, reminisce, and embrace, even after their mutual betrayal.
- In the Star Trek: Deep Space Nine episode "The Wire", one of Garak's many conflicting stories about his past has him and his friend Elim trying to frame each other for the same crime. Since Garak is Elim, it's not entirely clear what this is actually supposed to mean.
- The Hustle episode "Picture Perfect" ends this way. In the episode, Mickey's team promises a forger a cut of their scam if he forges the fake Mondrian they need to make it work. The forger is already under a fraud investigation and pretending to be unfit to stand trial; he also says that in order to do make the forgery convincing he needs them to steal him a real Mondrian to study. When they go to pay him off, he says that if they don't give him all the money he'll report the theft of the Mondrian, but it turns out that Mickey let the investigators who are after him know that he's faking his medical problems.
- In the Red Dwarf episode "Justice", Lister is being chased by a simulant, and they agree to meet face to face, without weapons; both violate the agreement. Lister's lead pipe isn't very impressive beside the simulant's knife and BFG. Good thing for him that they're meeting in a "justice field", where any crime you try to commit is inflicted on you instead...
- Played for Laughs (as usual) in Get Smart when Max and Siegfried meet to trade a prototype secret weapon for the return of the kidnapped Chief. Max hands off a dummy prototype and discovers that Siegfried gave him a dummy Chief.
- Supergirl (2015): Queen Rhea and her Daxamites attempt to invade Earth. Supergirl challenges Rhea to Combat by Champion. If Supergirl wins, the Daxamites must leave, and if Rhea wins, Supergirl will not interfere with their conquest. Despite agreeing to an honorable duel, Rhea cheats by using kryptonite and orders her fleet to attack Earth in the middle of the duel. Despite the kryptonite, Supergirl wins, but Rhea refuses to call off her fleet. Supergirl then reveals that in case she lost, she prepared a bomb that would saturate the atmosphere with lead particles (lead is like kryptonite to a Daxamite). The bomb is detonated, killing Rhea and forcing the rest of the Daxamites to leave Earth.
- This is standard procedure when two heels are going up against a face in a triple threat match, for obvious reasons. The heels always double-team the face at the start of the match... until one of them goes for a pinfall, the other pulls him off, they argue and then start fighting. When this happens, the face usually wins.
- One of the best examples is the Triple Threat match between Edge, Randy Orton, and Shawn Michaels in 2007. Before the match Edge and Orton, who were heel tag team partners, pledged not to fight each other during the match, and actually avoided this for the first 3/4ths of the match. When they finally turned on each other, they both tried to calm the other down, turned away to lure the other into a false sense of security, and started whaling away on each other.
- In Measure for Measure, Angelo tries to get Isabella to sleep with him in exchange for the life of her brother. She convinces his old fiancée to go instead under a Paper-Thin Disguise. He doesn't notice the difference but orders the execution of her brother anyway.
- Tosca has a very similar set-up: Scarpia tells Tosca that, if she sleeps with him, he'll tell the firing squad executing her lover Mario to fire blanks. After he sends out the order, she stabs him instead; it turns out that the order was to execute Mario normally anyway.
- Love's Labour's Lost carries this to the point of absurdity: the Prince of Navarre and his three attendants all swear an oath to stay away from women for three years, and all independently break it. The scene where this is discovered has three of them, in sequence, trying to guilt-trip those who've already had their oathbreaking revealed, only to be themselves exposed.
- In the last Genoharadan quest in the first Knights of the Old Republic, you challenge Hulas to a duel. While he tells you to Come Alone, he brings a small army of assassins with him and makes fun of you for listening to him. If you bring your party members along he hangs a lampshade on this trope.
- If you decide to side with Card-Carrying Villain Charnel or Smug Snake Stratos in the Sacrifice campaign, the two of them are the last two gods left by the penultimate mission.
Stratos: We both knew this alliance would end, and we've both been preparing for it. Now let's see which of us has miscalculated.
- Angel Moxie, in these three strips.
- Schlock Mercenary has the mercenaries attempting to lure Breya's troops on board so they can capture her, while Breya attempts to get her troops onto Tagon's ship so they can take it over. Plan B... err C ensues. Then Tagon's employer shows up. Backstabbings all around.
Breya: We worked well together! We used to be friends! Is this how you repay that?Tagon: You know, you'd be wracking my poor heart with guilt if your marines hadn't just attempted to hijack my ship.
- In the final few episodes of the first season of Beast Wars, Optimus and Megatron initiate a truce. Of course, neither side believes the other will keep their word, so while they both stick to the letter of the agreement ("no weapons") they unashamedly violate its spirit; treating us to several slapstick fights and several humorous spying montages.
- Stewie and Bertram's first confrontation in Family Guy:
Stewie: You came unarmed?Bertram: As we agreed.Stewie: Admirable — but foolish! (pulls out a gun)Bertram: (immediately pulls out his own gun)
- At one point in Samurai Jack, Big Bad Aku decides to skip the mooks and simply challenge Jack to a duel, provided Jack does NOT use his holy sword, the only thing that can kill him. Jack agrees as long as Aku maintains a human form and does not use magic or minions to cheat. When Aku begins losing the duel, he starts cheating by blasting Jack with magic. Jack reveals he knew this would happen and reveals he buried the sword near the duel site—along with many, many replicas.
- Truth in Television with online dating: Both sides always lie and feel betrayed when they learn "SexyModel346" lied too.
- Also for any instance of mutual adultery. Shows up both in real life and in literature. The Great Gatsby is an example of the latter.
- It has happened that a couple each had their online lovers, made arrangements to meet, and discovered that their online lovers were their own spouses. Unlike Escape (The Pina Colada Song), this has invariably led to hostile divorces.
- John Birmingham's (mostly) non-fictional He Died With A Felafel In His Hand: He and his housemate fall in love with the same woman, draw up rules of engagement for pursuing her and immediately start to break them.
- Hitler and Stalin in World War II.