Subverted in Dante's ending in Marvel vs. Capcom 3, where Mephisto appears before him and offers to revive his mother and fix his relationship with Virgil. Dante, being too smart to fall for such things, aims Ebony at Mephisto's throat and retorts:
Dante: I'm not really interested in mending fences with my brother, so here's my counteroffer: You give me a job that can pay my electric bill for the year, and I'll leave you here with your head attached to your body.
Mephisto: ...Actually, there's a fiend called Blackheart who has caused me trouble to no end.
Fear Effect has Mr. Lam do this with the King of Hell in order to get rich quick. Unfortunately, he has to raise a girl who is supposed to destroy the world. Naturally, this deal comes back to bite him and bite him hard.
Do you know what the funny and ironic part about this is? When the girl, who is effectively the Anti Christ, finds out about the deal and the terms, she calls out Mr. Lam on making such an evil and stupid pact. Yes, even the Anti Christ had moral objections to this!
This is how most of the bosses in the Mega Man Star Force games become bosses in the first place.
Subverted in Persona 3; the contract the main character signs with Pharos in the opening sequence practically screams Deal With The Devil — but despite granting the main character the services of the slightly creepy Trickster Mentor Igor, the contract in itself has no negative repercussions (it turns out to be implicitly vital in saving the world, in fact). Furthermore, the only condition on your side of the contract is to accept the consequences of your actions. Nothing more.
In Persona 5, each character's Guardian Entity first manifests as a Magnificent Bastard version of a character's own voice offering them a "contract" for power, in exchange for unleashing their hidden vengeance / rage / etc on the people and society that's wronged them.
In Mask of the Betrayer, the expansion pack to Neverwinter Nights 2, at one point you have to free a wizard who struck a deal with the devil and 'just signed it'. The resulting conversation and comment options while you comb the fine print of the contract and question both the devil and the wizard about it are close to being the most hilarious in the game.
Faras: So you have some experience with infernal beings, then?
Player Character: You could say that. I once knew a warlock who collected them, actually,
Interestingly enough if you dig completely through the contract and both sides of the story you can find that the devil a) cheated and b) doesn't realize it. He is forced by his very nature to declare the contract void if you point it out.
Alternatively, a Spirit-Eater with a very high Appraise skill - or an eagle-eyed player - can notice that a word is misspelled in the contract, rendering it nonbinding under infernal law. Pointing this out to the devil causes him to meekly leave the plane.
Mask of the Betrayer also has Oronock and Thael'ka, a pair of Devils who've set themselves up as merchants to control the trafficking of souls between hell and a wizard's academy.
In the original campaign, this trope was played straight by Ammon Jerro, who sold his soul to the Devil Levistus. Jerro's ally Mephasm subverts this, however; he'll reject buying your soul if you offer to sell it to him, and only seems interested in trading magical artifacts.
In both forms. Not only does the small print state that "Your soul is mine", but you can attempt an ordeal to recover it. The song used for that final battle? The Devil Went Down To Georgia.
In Soul Nomad & the World Eaters, After failing a Demonic Possession of the main character, Gig, who is now fused to your soul, offers the main character a Deal With The Devil: He'll lend you some of his divine powers in return for limited control of your body, allowing you to create your army. During certain points in the story, he'll offer you better access, granting you incredible powers that will allow you to grind whoever you're facing into fine powder... But once you're done with said grinding, you get a Non Standard Game Over as Gig uses that access to boot your soul out of your body and takes it for himself.
In Half-Life, the GMan takes the liberty to conscript Gordon Freeman into his service without ever offering him a choice or actually informing him about it until the end of the game. In both this and Half-Life 2, he's constantly around manipulating events to turn out favorably for Gordon and his allies. Episode 2 informs us that he did the same to Eli Vance. Instead of forcing them to do the work for him, he arranges it so that by achieving each of their own goals, they actually further his own hidden agenda.
In Final Fantasy XII, Ashe is offered the chance, by the deities of her world, to cut some pretty shards from a big crystal. These shards are weapons of mass destruction, and with them she could become Queen of the World - the problem is, it's implicit that if she were to do that, the deities would have indirect control over mankind through her. The deities present her with apparitions of her late husband to tempt her. Ultimately, the crystal is destroyed before she can truly decide.
It's implied that the most famous King who 'united' the world and left three of those shards as his legacy actually did the deal good and proper.
Subverted with Auron, who is offered a deal to get out of Hell, and refuses, and then gets out anyways.
Auron: "This is my story, and you're not part of it."
Subverted early on in Shadow of Destiny: Eike assumes that the Homunculus is after his soul, but Homunculus isn't interested. One possible ending double subverts this, implying that the only reason Homunculus doesn't want Eike's soul is that he already owns it.
In Dark CloudSeda makes a deal with a Robed man, by infusing the blood of witches in him, he would gain immense magical power to aid him in winning the war he was in to protect his kingdom, however there was a price: When his hatred and sorrow peaked; the Dark Genie was born.
In GrimGrimoire, Lillet Blan proves herself to be a Guile Heroine by making complete mockeries of two Big Bads, both of which had only been sealed before since they were too powerful to defeat. She does this by abusing a very big loophole — on HER side — in a Deal With The Devil, a loophole which Hell's lawyers are probably going to need to patch to standard contract procedure in the future...
In case you didn't know, she just conned one Big Bad into killing the other Big Bad (by summoning him outside of the first Big Bad's bindings), then sold her soul to the surviving Big Bad for one wish, in a contract that is only breakable if the demon volunteers to be sucked back to Hell and tortured for eternity. Her wish? She asks the demon to embrace God.
Grimlet:(realizing to his horror that he'd just been suckered by a little girl) Mephistopheles... is this your doing? Advocat:(laughing like a maniac) No. But, I so wish that it was.
Richter Abend from Tales of Symphonia: Dawn of the New World struck a deal with the demons of Niflheim (the land of the dead) for enough unholy power to avenge his best friend. Since the target of his revenge is also the seal that stops the demonic populace from invading the world, and the absence of the seal would allow aforementioned best friend to come back to the world of the living, it works out quite well for all concerned. Except Richter is planning to double-cross the demons by turning himself into a new seal after his friend is reborn.
In Fire Emblem: Path of Radiance/Radiant Dawn, mages sometimes entice spirits to enter their bodies, giving them great power... for a price... Such mages are called Spirit Charmers, for obvious reasons. While the spirits themselves are not diabolical, the effects of charming one are. (Supposedly...)
The Dark Meadow uses this as the main backstory in the game. Suffering from a terminal illness, Ben Jacobi's parents sell their souls in order for their son to be cured of his illness and receive 17 great years afterwards. 17 years later, an overwhelmingly successful Ben feels invincible and thus agrees with the Trickster to sell his daughter's soul so he could live for another 17 years. His wife never gets over their daughter's subsequent abduction and divorces him, leaving Ben as a penniless, drunken mess. Ben's time is nearly up once more, hence why he's in the hospital.
Twisted on its head in Planescape: Torment with Fhjull Forked-Tongue, a devil who tried to tempt a fallen angel with a deal... only to find that said angel was considerablydefter at contract manipulation than he, with the end result being that he's forced to be good for as long as he and the angel remain alive (both are, naturally, immortal). It goes without saying that when you meet him, he's not having a happy existence.
Played straight in the same game should the Nameless One come across the Grimoire of Pestilential Thought. It offers rather cynical wisdom such as "There are two secrets for becoming truly powerful. The first is to never tell anyone everything you know." But, it can teach you powerful spells, at a price. It starts off just wanting a drop of your blood, but it then demands you sell one of your party members into slavery. Finally, in exchange for "Power Word: Kill", you must murder another one of your party members.
In the same vein, The Dustmen will let anyone sell themselves into a contract where their body is reanimated into a zombie, then a skeleton, for work in the Mortuary. In the Hive you'll find someone upset that they sold their body after death and want the contract back, a zombie holding a note that says "Please cremate me after death - take this magic item in exchange", and the Nameless One himself can sign such a contract - three times over!
When visiting the Sensate Hall, you can attend a lecture from Ghysis The Crooked, one of the veterans of the Blood War - an all-consuming war taking place on the lower planes since time immemorial. He offers advice on how to stay out of it, and asks everyone there to lead a good life so that they won't fall to the lower planes in death and be conscripted into the war for eternity. If you've asked Verusika about him, though, you can get Ghysis to tell his story on how he got out...
Ghysis The Crooked: "Me an’ two other lads fled like dogs, that’s what ‘appened. We scurried across the Plane fer a handful o’ days afore we came to this great pillar o’ livin’ ‘eads… an awful sight, it was... they jabbered an’ hissed at us, callin’ fer us ta come closer. That night I stole away from the others an’ went ta talk ta th’ pillar." Ghysis shut his eyes and rubbed at his temples "I… I asked this pillar ‘ow I might be freed, ‘ow I might escape Baator... an’ it told me in exchange fer th’ two o’ my brothers." He was quiet for a moment, biting on his knuckles as if fighting back tears “Ta me... at th’ time... t'was just math."
Eventually, The Nameless One can come to the Pillar of Skulls himself. The pillar promises to answer all your questions - with a dear price for each answer. For every answer, it demands one of the following before it answers your question:
Placing Morte back in the Pillar though you can break him out later - you'll lose some max HP from all the skulls biting you, and they'll refuse to answer any more questions - instead yelling for abashis to come tear you to ribbons.
The location of Fhjull Forked-Tongue which you can get aways with lying about if your Charisma is good enough, essentially paying nothing.
The Modron Cube which is immediately and irrecoverably destroyed
Fall-From-Grace if you choose her, she will assume you're joking. If you confirm you're serious, she will dissappear into thin air, never to be seen again. The Pillar doesn't accept this, given she escaped and all.
Annah if you choose her, she'll assume you're joking as well. Confirming you're serious will make her fight you to the death. The Pillar doesn't accept her corpse.
The blood of an immortal (yours) Picking this will result in hundreds of skulls biting you and draining your blood, making you lose a lot of max HP.
In addition, if you ask "Who am I?" to the pillar and Vhailor is in earshot, when Vhailor hears the answer he will fight you to the death for your many injustices.
Castlevania 64 offers a very interesting variation. In the Villa, the heroes encounter a demon salesman called Renon who offers to sell you potions and other items. (His stock is not very impressive compared to most merchants, but unlike most, his shop can be accessed from anywhere, using magical scrolls, making him somewhat of an asset.) However he neglects to mention that spending more than 30,000 gold in his shop equals to selling your soul to the devil (that clause is technically written into the contract, but in a demonic language that humans can't read), in which case Renon will be more than eager to claim his fee when the time comes. (If this happens, you have to fight him as a Bonus Boss, and the contract is rendered void if you defeat him.)
Castlevania: Dawn of Sorrow features the Devil Soul. It's a familiar soul - press R and you will begin to lose ten HP a second in exchange for much higher power. It'll stop before it kills you though. Great if you're good at not getting hit or if you're doing a Boss Rush.
In Neverwinter Nights: Hordes of the Underdark, the Valsharess hasn't to her own mind even made a deal with the devil, but simply made him her servant (somehow). However, considering he is an archdevil called Mephistopheles, she should have known it was not going to end well. There are rules, whatever they may be, and eventually he uses the player character to manipulate her to break them enough that he can bend the bounds of her control and have her killed. Then, since he now happens to be in the material world, he sets out to conquer it. Later, he may simply talk the player's companions into joining him before the final encounter.
It is even hinted that the entire "deal" was an Evil Plan by Mephistopheles himself, started as far back as the previous game.
Shadow Hearts has as a major plot point in Covenant that mortals can make pacts with the three most powerful demons in that universe: Amon, Asmodeus, and Astaroth. Doing so will let the demons eventually hollow out your soul and take up residence. Yuri Hyuga, who made the pact with Amon, is in no danger because he simply beat Amon into submission. Nicholai, who made the pact with Astaroth, had enough willpower to stop the Demonic Possession... until he got captured by another faction of bad guys and was tortured to the point where his spirit broke.
The game also has a variant on this in Zant, who sells his allegiance to Ganondorf in exchange for the latter's help in usurping the throne of the Twilight Realm. Zant, mistakenly believing Ganondorf to be a god, can't be killed as long as the immortal thief-lord lives, but in exchange for the Twilight throne, Ganondorf forces Zant to turn his people into monsters and invade Hyrule. (Zant didn't really need much persuasion on that matter, though.) In the end, this deal backfires on Ganondorf when he tries to reach out to Zant for power to save him from dying, but a disillusioned Zant opts to kill himself instead by snapping his own neck, taking Ganondorf with him.
God of War: Kratos makes a deal with Ares to save his life. Then Ares tricks him into murdering his wife and daughter. (More) Killing ensues.
Kratos: "ARES! Destroy my enemies — and my life is yours!"
Kratos manages to get out of this deal in a rather badass way — by absorbing the power of Pandora's Box, growing to Godly size, and killing the hell out of Ares - becoming the new God of War.
That said, he still ends up the loser. Driven to madness by what Ares had him do, he prays to the other Gods to make his nightmares stop. Athena agrees to forgive his deeds if he somehow stops Ares. After Kratos slays Ares, Athena honors the agreement and forgives his deeds. Unfortunately for Kratos, she never agreed to stop his nightmares. This drives Kratos to suicide. Which Athena refuses to let proceed - as there is an empty chair on Olympus for the new God of War.
Dragon Age has numerous demons all seeking to makes deals with everyone, especially magi. They will keep their word, but are usually pretty jerkassy about how they do it. And after the deal they generally turn you into an abomination and take over your body. Strangely enough, it's actually the better way to become possessed because it leaves your will intact (as opposed to the demon crushing your spirit) because then the control can be broken. As proved with Connor.
This is how one becomes a blood mage.
Connor himself made a deal with a demon to save his father after he was poisoned.
The protagonist and/or Alistair's deal with Morrigan to not die killing the Archdemon has the distinct scent of this trope about it. Its all about the way she presents it, combined with ominous camera angles and background music.
Dragon Age II also has two party members who have made such deals with all the best intentions. Merrill made a deal with a demon to become a blood mage so that she could help her clan rebuild its former glory. Anders made a deal with the benevolent Fade spirit Justice; Justice could possess him, preventing Justice's death and augmenting Anders's powers...but, since Fade spirits are essentially creatures of emotion, his own anger at the Templars and the injustices he saw in the world corrupted Justice into a demon of Vengeance. Both end up suffering greatly for their poor judgment later.
The Reapers in Mass Effect often make use of humanoid aliens to assist them in their repeating genocides of all galactic civilizations. Since they know that nobody would willingly help them or even be fooled by offers to be spared for their help, they instead rely on Indoctrination, distorting the minds of all sentient creatures within several dozen kilometers around them to make them see the Reapers as trustworthy and not all bad. While it has only limited reach and takes time, strong individuals can retain their personalities and abilities almost intact for quite a long time, making them extremely valuable to infiltrate any group that might be a real problem in the next coming extermination. At shorter range, even small parts of dead Reapers still have that effect after millions of years.
Sovereign approached the geth prior to the first game, offering them what they most desired in exchange for their help slaughtering the galaxy. Only 5% of the geth accept the offer, the majority believing that they must earn what they want most by their own hands, not rely on the charity of others. Whether Sovereign intended to keep its promise is unknown, but given Reaper behavior in the rest of the series, they probably would have betrayed the geth anyway in the end.
In Mass Effect 2, the Illusive Man does not fall for the story that the Reapers would spare anyone who surrenders to them. Instead he believes that the Reapers are just machines and that they can be controlled if one has sufficient knowledge of their technology. To him the potential of Reaper technology is too great to allow it to be lost, and so he fights those who would destroy them, greatly weakening the resistance the Reapers are facing in their invasion. Unfortunately, it turns out that in Mass Effect 3, all of the Illusive Man's Magnificent Bastardry is not enough to keep him and most of Cerberus from being indoctrinated.
Used in Bayonetta, as the Umbra Witches, including the heroine, gain their power from making pacts with Infernal powers. As a consequence, if and when the Witches die their souls are Dragged Off to Hell. Presumably the Lumen Sages, as the counterparts to the Witches make the same kind of deal but with different entities, but it's not really elaborated upon.
Happens to the main character in Breath of Fire: Dragon Quarter. When struck down by his rival Bosch, the dragon Odjn restores your character's life and gives him the power of the Wyrm. From then on, during any battle he can call upon the Wyrm's power and do tremendous damage to anything in his way. However, every time he does so, the Wyrm takes over more of his soul. When the Wyrm takes over his soul completely, it bursts out of his body, ending the game. Later on, Bosch gets a similar power from another dragon.
In The Legend of Spyro trilogy, the Apes made a pact with Malefor to free him from the Well of Souls in exchange for power. Well they work their butts off to free him and he 'rewards' them by turning them into undead skeletons forever condeemed to live in the dark.
StarCraft II has this going on between Tychus and Arcturus. No points for guessing who the devil is.
Arcturus: They say a man doesn't know anything about himself... until his freedom's been taken away. I wonder... how much do you know about yourself? Adjutant: Please step onto the platform. Arcturus: Convict 626. Murderer. Pirate. Traitor. Today, you go free. But as you'll soon learn, even freedom has its price. *cue various machines assembling a Marine suit on Tychus* Adjutant: Combat suit sealed and locked. Arcturus: You will carry your prison with you. That armor will be your new cell. Make no mistake. War is coming, in all its glory and all its horror. Mister Findlay, your freedom awaits. Tychus: Hell, it's about time.
The actual deal, meanwhile, goes something like this: Mengsk will let Tychus go free if and only if Tychus assassinates Kerrigan for him. Until then, he's allowed to join up with Raynor and his rebel army, albeit in a suit of welded-shut powered armor... which can, incidentally, be remotely commanded to shut his major organs down if he ever disobeys orders.
In Fate/stay night Alaya, the will of Humanity to survive, is capable of making deals with humans. In exchange for a miracle granted via Alaya's power, the human agrees to become a Counter-Guardian in death. Counter-Guardians are dispatched to destroy threats to humanity, which more often than not are humans themselves, and destroying anything associated with the threat, up to and including entire nations. The only way to escape the contract is if the Counter-Guardian's legend becomes revered enough for them to enter the Throne of Heroes.
Archer entered a contract to save a few hundred people from a natural disaster. He despises his existence as a Counter-Guardian, as even though he is saving more people in the long term, all he ever sees are the people he slaughters indiscriminately.
Saber regretted her choices in life and made a contract with Alaya. In exchange for undoing her choices, she would become a Counter-Guardian. Prior to death, her soul was removed from time and sent to claim the Holy Grail, which could grant the wish. She ultimately chooses to accept her life, and so is freed from the contract.
In an Etna mode chapter break in the Updated Re-release of Disgaea, she offers to beat up bullies harassing a 7-year old kid, in exchange for the kid's servitude after he dies. Seeing as this is Etna, a nearby prinny immediately objects.
He's not exactly the devil, but in Avernum 5 the mysterious mage Gladwell is certainly willing to offer you a deal. Just for agreeing to work for him, every party member will get an additional point to every primary statistic (a significant boost in power), plus powerful magical items in return for every artifact you bring him. The catch is that this power comes with his control—if he wants you to get him an artifact near your current location, you'll be physically incapable of proceeding until you get it, regardless of whether stealing the artifact will piss off a town and prevent you from completing further quests there. He cannot, however, prevent you from physically attacking him . . .
He's back in game 6, and this time he's a bit more subtle. He tells you he'll reveal his goals to you once he trusts you more, but in the meantime you'll just have to take his word for it that he has a good reason for telling you to go to various places filled with powerful undead and set them loose. As early as his second mission you can attempt to warn people about what he's up to, but you'll find that your jaw refuses to obey you.
Before the story begins in Eien no Aselia, Yuuto somehow managed to make a contract with Desire, a living weapon. The deal was that it would save his little sister's life, and when the time came Yuuto would wield it to destroy its enemy, Oath. Both swords are evil. Played with a little in that Desire never really gains the degree of control over Yuuto that it expected it to. And that it dies before achieving its goal and lightens up a little at the end.
Close to the end of Oni, Konoko discovers that Muro is planning to pollute the environment worldwide to kill everybody. However, he will save people who sell their souls to him for a Daodan Chrysalis. On their part, they will survive the polluted with a Daodan Chrysalis implanted in each of them. On Muro's part, he gets people who will serve under him, and will kill and destroy on his command, which would make them as monstrous as him. If that is not a Deal With The Devil, then what is?
Towards the end of Mortal Kombat 9. Raiden tries to make one with Quan Chi to help turn the tide against the Big Bad after Sindel's massacre; the souls of all those killed in the battle for Netherrealm's aid. Unfortunately, the Big Bad had already sold all the souls to Quan Chi.
In The Elder Scrolls, the Daedric Prince Clavicus Vile loves making deals with mortals that they later come to regret, though in Oblivion, he makes a deal he later comes to regret, in acquiring Umbra. This results in him losing some of his Daedric power. Though Clavicus Vile is indicated to sometimes make agreements that the recipient doesn't regret (this probably has something to do with the fact that unlike most devils, he actually has a fairly strong conscience. It just happens to be external).
Skyrim shows that Nocturnal also likes cutting deals. specifically she grants you special powers and badass armor, along with largely free reign in return for protecting her shrines in life and death.
The first Werewolves sold their souls to Hircine in exchange for their power. When a werewolf dies, his or her soul is doomed to join Hircine's eternal hunt. Some werewolves see this as a curse, and wish to be cured. Others see it as a blessing and offer it to those they deem worthy.
In Dawnguard it's revealed that making a pact and submitting yourself to Molag Bal will turn you into a more powerful Vampire than simply letting the disease that leads to vampirism run its course does. The Big Bad of Dawnguard did this long ago to stave off death, draggin his wife and daughter into it and sacrificing many of his own subjects in the process.
In Dragonborn, Miraak, the First Dragonborn, gained the power he needed to defy his former dragon masters through a deal with Hermaeus Mora. The player must make that same deal in order to gain the power necessary to slay Miraak.
In fact, depending on how thorough you are, by the end of the game you may have pledged yourself/sold your soul to around ten different gods.
A major plot point in the Hearts of Stone expansion of The Witcher 3. A noble by the name of Olgierd von Everec made a deal with a powerful demon known as Gaunter O'Dimm in order to regain his fortune and keep his fiancee from being married off to another man, but later on refused to surrender his soul as part of the deal. Geralt is forced to make a deal with the demon in order to save his own life, and in exchange has to help O'Dimm fulfill the terms of the contract with von Everec. Later on Geralt can learn how to banish O'Dimm by gambling for his and von Everec's souls, but if he fails they both die.
The winner of Twisted Metal gets one wish from Calypso, when he grants it things aren't always what they'll expect.
In Twisted Metal Black though, the wishes have to malicious in nature to not be twisted as we learn.
In The Binding of Isaac, Devil Rooms sometimes appear after boss fights. Inside these rooms, Isaac can trade hearts from his Life Meter for extremely powerful items and upgrades.
There's a few of these in Odin Sphere. Ingway makes one with the queen of death herself for a power to get revenge on Odin in exchange for his soul. It seems something similar happened with the same power to Cornelius's grandpa when his home country was being invaded many years ago. Oswald is tricked into one by Melvin by not being told that using the demonically powered blade he uses will eventually deliver his soul to the queen of death when he dies. However, all three of these don't go as planned. Ingway doesn't actually die until the queen of death is dead and can't collect.Cornelius' grandpa got free during the end of the world and took the place of the queen of the dead.Oswald is ultimately saved from his fate by Gwendolyn when she goes down to the underworld to get him back and kills the queen of death herself. He's also rescued the first time by Odin but he ends up making a deal with him in exchange for Gwendolyn. This one is foiled by Gwendolyn herself when she decides not to give the ring to Odin because Oswald gave it to her as a sign of his feelings for her. Odin also failed to add in the deal of giving the ring up because he only asked for the death of a dragon that originally had it, which was carried out. The parties that would normally benefit all get screwed over. Except maybe the case of the Fire King who does get screwed over but would be consider the usual sucker in these types of deals.
In Don't Starve, In Wilson's character origin video it reveals that he agreed to build a machine for Maxwell in exchange for ultimate scientific knowledge. The machine is what ended up stranding him in the Don't Starve world.
Murphy Pendleton in Silent Hill: Downpour strikes a deal with corrupt corrections officer Sewell to get revenge on the pedophile who killed his son in exchange for a favor. Said favor turns out to be offing benevolent corrections officer Coleridge.
Subverted in Borderlands. The final DLC introduces Mr. Blake of the Hyperion corporation, who talks with an Evil Brit accent and is introduced with horn-like prongs in his hair and a ring of fire around him. He serves as your questgiver (offering you vast amounts of money in exchange for ending a Robot War they started accidentally started while trying to kill you). Despite all these hints, he doesn't betray you and pays you well for your services. In the sequel, where his boss is the Big Bad, it's revealed he helped Dr. Zed escape from some assassins Hyperion sent after him.
In Warcraft3, Grom Hellscream and the rest of the Warsong clan drink the blood of Mannoroth and use their restored chaos-empowered strength to slay the demigod Cenarius. This puts them under the thrall of Mannoroth again. When Thrall confronts Grom, the latter confesses that the Orcs were not forcefully corrupted by the Burning Legion as Thrall always believed. Grom and the other chieftains gave themselves and their clans willingly to the Legion, and drank Mannoroth's blood.
Kel'Thuzad assumed this was how the Lich King had come to control the Nerubians. When he mentions as much to Anub'Arak, he's told that "Agreed implies choice."
Twisted a bit thanks to the ambiguous nature of the 'demon' in Shadow of the Colossus: Wander brings the corpse of his love to a forbidden temple and strikes a deal with the power sealed there (Dormin): slay the sixteen Colossi, and Dormin will revive Mono. Exactly what Dormin is never fully gets explained, but Lord Emon and his men treat Dormin like a horrific demon, and Dormin's true form being a giant horned Living Shadow and taking over Wander's body don't exactly help Their case. That said, Dormin does keep Their end of the bargain: in the end, Mono is resurrected, just as They promised, and the fact that They say They're "borrowing" Wander's body implies They were going to give it back at some point. Not to mention They actually warn Wander that dealing with Them might not turn out well for him in the end, which is uncommon behavior for a demon, to say the least.
The Secret World has many examples of characters who, whether directly or indirectly, were offered opportunities in this spirit from the beings behind the filth. The players are offered such opportunities at some points, and fight other characters who have done so.
In Mario & Luigi: Dream Team, Bowser and Antasma make a deal with each other. Bowser gets Peach, Antasma gets the world. If it's not immediately clear who the devil here is, it's Bowser(not suprising since he's the Great Demon King).
When you finally confront the Dragon in Dragon's Dogma, he reveals that he's captured your "Beloved" as determined by the in-game Affinity System and offers you the choice of either facing him in battle or sacrificing your Beloved, in which he will willingly leave Gransys and leave you as an immortal with a claim to the Duchy. He reveals that Edmun Dragonsbane, the current Duke of Gransys took the deal. However, accepting said deal results in a Non Standard Game Over.
The DLC content of Total War: Shogun 2 features a new building called Lend Lease. Taking it gives you an immediate one-time lump sum of 4500 gold, but permanently dents your Daimyo's honour rating. Being in league with the invasive Portuguese is bad enough, but is it really worth publically pissing on the tenets of Bushido and Buddhism AND spreading sentiments of betrayal among your generals, just for a quick injection of cold, hard cash?
In one wizard's lab in Avencast: Rise of the Mage, imprisoned demon Kulkurazz will trade his ability to open one door for his freedom. Having satisfied the arrangement, both you and Kulkurazz go your separate ways...until he reappears late in the game to exact vengeance. By getting a fair deal from a demon you were ripping him off, and his pride won't allow it.
Fallen London: Any sort of deal with the Masters of the Bazaar that goes beyond purchasing stuff for actual money tends to resemble these, mostly because they have a bad case of Blue and Orange Morality and have no idea how humans work. Actual devils are a lot more straightforward; their deals are more or less monetary transactions where your soul's the currency.
Cuphead: The game starts with Cuphead and his friend Mugman losing a game of Craps against the Devil. Just as he's set to kill them, they plead for their lives and he agrees in exchange for doing deeds for him.
It's eventually revealed to be what caused the destruction of the city in which the game is set, thanks to a demon invasion. When she was younger, the sovereign, Queen Katarina contracted an incurable disease. Gabriel, the only healer able to help her didn't do it with medical means but by making her sign a demonic pact with her own blood. It granted her complete recovery, but they will come back to get her thirteen years later. To avoid this, Gabriel taught her a spell making the demons unable to locate her. It had an unexpected consequence: since they couldn't find her, the demons turned against the whole population.
The protagonist, Victor Vran, received his demon powers this way. He was a prince. His lands where threatened with an invasion which would have been impossible to vanquish. He made a pact with dark powers and received his demon powers, which he used to repel the invaders. It ended cursing the land he was ruling, forcing him to leave as a wanderer to make sure he would taint any land by residing in it too long.
It ends to have some importance in the story. A part of the plot consists in looking for Queen Katarina's pact to cancel it. It's also revealed that Gabriel (under a false identity) is the one who also proposed the pact to Victor...
In Galactic Civilizations, the Korath Clan (a group of Drengin), made a deal with the Dread Lords to gain vast power, in exchange for helping the Dread Lords annihilate all other intelligent life. The vast power comes in the form of biological adaptations (it's arguable whether the Korath Clan are even the same species as the Drengin after a while) and highly advanced technology. It's implied that the Dread Lords plan on exterminating the Korath as well once they're done, though.
In Gardens Inc.: From Rake to Riches Jill's friend and assistant Mike agrees to use his pickup truck to transport some unspecified "merchandise" for Cliff Gold, who's been sabotaging their gardening company the entire game, in exchange for Gold supposedly fixing the town gardening contest so Jill wins it and the cash prize, paying back the money her grandparents owe to Gold and thereby saving the family villa.
In Undertale, playing the No Mercy route ends with the entire game world being erased and the first child offering to reset it if you give them your soul. Accepting the offer lets you play through the game again, but it permanently turns the game's Golden Ending into a Sudden Downer Ending.
In Pony Island, you play the eponymous Game Within a Game multiple times, and are usually interrupted after a few levels with a screen saying "Experience the rest of Pony Island! Insert your soul to continue" after a few levels.
In Guitar Hero 3 it is reviled just before the final concert that the Manager that gave you a Record Contract is the Devil and a part of the Contract was the band give their Souls to him.
Once upon a time in RuneScape, the Mahjarrat Sliske promised power to six generals who needed it to battle the vampires of Morytania. They won battle after battle... and on the eve of their final confrontation with the vampires, Sliske murdered them himself and turned them into the Barrows Brothers. He'd never promised them victory, only power.
Sliske gains another Barrows wight in "Kindred Spirits" by offering Linza the blacksmith protection from the Dragonkin she'd robbed for supplies, in exchange for becoming a wight after death. He never promised not to kill them himself.
Yet another Sliske moment: a dying man named Gregorovic prayed to Sliske to save him from his terminal illness. Long story short, Gregorovic is now an insane Monster Clown that eats people to stay alive.
Among the Signature Heroes, Ariane the mage tried to scam a demon once. The demon had offered her information in exchange for a blood sacrifice to Zamorak, and Ariane used her Seer powers to learn the demon's secret without making the cut. In retaliation, the demon convinced bystanders that Ariane really had made an offering, getting her expelled from the Wizards' Tower.
In the Player-Owned Port, amateur adventurer Meg sometimes asks for advice about dealing with demons. The best-scoring advice is "don't risk it", though if she's already made a pact you can advise her to check for loopholes.
In Charlie Murder, Paul Bitterman strikes a deal with dark forces after being kicked out of the titular band, becomes the powerful Lord Mortimer, and forms the Death Metal band Gore Quaffer to take Charlie Murder down. You need to expose the demon possessing him to get the good ending.
The Elder Power Tlacolotl in Nexus Clash runs a giant pyramid-scheme demonic organization run on this trope. You never deal with him directly, but if you join his side everyone who may scam you in a devil-deal is themselves a victim of a larger Deal with a greater demon, and so on all the way up to Tlacolotl himself.