Of all the evil entities, Mephisto, the Marvel Universe's version of Satan, is the major example of these trope. It's his trademark. Mys-Tech, the Big Bad of Marvel UK's 1990s books, are immortal sorcerers who made a deal with Mephisto a thousand years ago. Come the end of the 20th century, they found themselves sinking into debt, with ever-increasing payments of souls required. Their desperation fuelled many plot lines — and, years later, Revolutionary War saw Mephisto try to close down his end of the deal.
Black Panther: Subverted. The Black Panther pledged his soul to Mephisto (yes, that Mephisto) in exchange for Mephisto agreeing to depower an enemy of the Panther's that he had given great demonic power to. Mephisto lived up to his end of the bargain, and so did the Panther... but when Mephisto tried to claim the Panther's soul, Mephisto found that it was linked to the souls of the Panther God and every single previous Black Panther warrior in existence, whose sheer goodness threatened to destroy him. Mephisto requested that the Black Panther agree to release him from the pact, and the Panther agreed. This is probably one of the only cases where the Devil is the one who asks that the contract be voided.
Daredevil: In Daredevil (2022), the Stromwyns offer one to Mayor Luke Cage, who promptly tells them where to stick it.
Doctor Strange: Baron Mordo tried to obtain power by selling his soul to not one, but two powerful demonic entities, Mephisto and Satannish. He got greater power, but it wasn't enough to defeat Strange, and things got much, much, worse when both demons came to collect. Mordo had counted on Strange to save him, but the two demons started fighting each other over Mordo's soul, each one apparently willing to destroy the Earth before letting the other have it. (Strange managed to drive them away with a ritual that would have merged them together into the evil singularity they originally were, forcing them to flee to avoid it, and seeing as they haven't bothered Mordo since, the contracts he made with them seem to have been annulled somehow.)
Earth X: Subverted by Mephisto again in Universe X, when he offers Captain America a device that can spirit him away to an extratemporal limbo any time he's in danger of dying. In fact, Mephisto is counting on Cap rejecting it; the real temptation is for the Captain to reject offers of help and depend on his own abilities to a fault. He dies shortly thereafter, nearly derailing Mar-Vell's plan to defeat Mephisto and Death (and when Cap bats the device away, it activates and sets another temporal plan in motion). That Mephisto guy is catching onto this sort of thing....
Fantastic Four: Doctor Doom makes a deal with a cabal of demons in the "Irredeemable" story arc that involves selling his former childhood love's soul to them and wearing her skin as his new armor. He nearly defeats Reed thanks to his new power, but then he arrogantly claimed he wasn't subservient to any other power. The demons responded by dragging him into hell.
Ghost Rider: In the movie adaptation Ghost Rider (2007), Mephistopheles plays a little hard and loose with the rules in order for the plot to portray Johnny Blaze more sympathetically. He pricks Johnny's finger while Johnny is just looking the contract over (and thus did not give clear, informed consent), and the splash of blood counts as a signature. He then cures Johnny's father's cancer, but kills said father the very same day via a motorcycle accident. In the Ghost Rider comics, Blaze still made the deal with the devil, except the Ghost Rider is actually an angel. Thus, when Johnny dies and goes to Hell, he can and does escape. If he dies without the Ghost Rider, however, he still goes to Hell permanently.
During the brief period in The Incredible Hulk (1968) where the Hulk was separated from Bruce Banner thanks to the climax of Onslaught, the then-Bannerless Hulk agreed to become Apocalypse's new Horseman of War to rid himself of the shrapnel that's been in his brain since the events of "Ghost of the Future" and the hallucinations of Bruce's parents (especially of Brian Banner following the realization that Brain's death was an Accidental Murder by an enraged Bruce) and even Betty that he began to experience. While the shrapnel removal was successful, the hallucinations of Brian came back when he realizes he's seriously hurt Rick Jones while fighting the Juggernaut and Absorbing Man and the resultant horror causes him to ditch the gig (and armor).
Jason Macendale follows several demons back to their lair and offered his soul to N'astirh in exchange for power. However, N'astirh didn't want his soul, but decided that Macendale's effrontery was worth something even if his soul wasn't, and had him possessed, turning him into the Demogoblin.
Cameron Hodge makes a pact with N'Astirh to provide mutant babies to use in the demon's invasion of Earth. In return, Hodge is granted immortality.
The Infinity Crusade: Subverted by Thanos. Mephisto offers a key piece of information in subduing the Goddess in exchange for one of her cosmic containment units. When Mephisto later returns after the conflict has concluded to collect his payment, he decides to test his new toy against Thanos, only to realize that it is powerless. Thanos then clarifies that, while he had honored their agreement by providing Mephisto with a unit, it was never specified that he wanted one that functioned.
The Punisher: The Punisher: Born depicts Frank Castle's final battles in Vietnam before being sent back home, and has him stationed at a run-down base manned mostly by drug addicts and slackers. So when a massive Vietcong offensive comes, the base is quickly overrun. Before long, Castle is the last man facing hordes of NVC in close combat, and a voice that had coaxed him to accept an agreement throughout the comic returns forcefully. It rams home the concept that he can either die here, never to see his wife and children again, or he can accept its terms, which will require a payment but will allow him to continue fighting a war forever. As the combat reaches a brutal fever pitch and the voice is practically shouting in his head, the Punisher growls "Yes." Later on, when he meets his wife and kids at the airport, the voice returns. It casually reminds him that it had mentioned a price, and Frank sees Maria and the children outlined by the infamous Punisher skull.
Sleepwalker: A variant occurs when the demonic genie Mr. Jyn manifests on Earth by pretending to serve a human "master" and get back at those who wronged him, only to manipulate him into letting Mr. Jyn cause more and more mayhem until the demon is released in the process.
One More Day: Peter Parker allows Mephisto to save his Aunt May's life in exchange for undoing his marriage to the woman he loves, thus wiping away the last twenty years of his life. However, Mephisto doesn't bargain for Peter or Mary Jane's souls, and in fact tells them that he stopped making that deal ages ago. That's because the souls of those who made the ultimate sacrifice to save another suffer nobly for all eternity... "and really, where's the fun in that?"
Subverted in the 1990s by the Jason Macendale Hobgoblin, a B-list villain who had been struggling to increase his powers. During a demonic invasion of New York, Macendale seeks out the demons' leader and offers to trade his soul for power. In a ghoulishly ironic twist, the demon openly laughs at the idea, considering Macendale's soul to be too pitiful to be worth taking ("What would I want with your soul?" laughs the demon. "Have you looked at it lately? Disgusting!"), but goes ahead and gives Macendale the power of a demon anyway, just for making him laugh. Macendale's additional power makes him a more formidable opponent, even coming close to killing Spider-Man on a couple of occasions, but it also ends up making him go Ax-Crazy and turning him into a fanatical Knight Templar. Macendale isn't exactly a Butt-Monkey, but no matter what he tries to do to increase his powers, he just can't catch a break... (and then he gets turned into a cyborg. And then he gets killed by the original Hobgoblin... only for said original Hobgoblin to immediately retire and not do anything ever again for about ten years.)
Champions (2019): Miles Morales and Amadeus Cho make a deal with Mephisto to turn back time enough to save Kamala Khan and Viv Vision. However, this ends up costing a few civilians their lives. Mephisto ends up explaining to his son Blackheart that he loves making Spider-People suffer due to the fact that they give people hope and he likes to quash that.
Superior Spider-Man (2018): Otto makes a deal with Mephisto to return him to his original Doctor Octopus body when he is unable to battle Spider-Norman (a Norman Osborn with Spider Powers). He even claims he'll fix any mental disturbances his tentacles cause him since Otto claims that's why he went insane, though the way Mephisto phrases it, it was never the tentacles.
Edge of Spider-Verse (2022): Played with in Spinstress's story, where Norma the Fairy Gob-Mother offers her a standard deal for powers, but at the exchange that if she is unable to fulfil the terms of their contract by midnight, she will be unable to find love, though the fairy sees herself as being different from a devil, stipulating there are no "deals with the devil" clauses in the contract. Spinstress accepts, but is unable to fulfil her part of the bargain. Then, in Edge of Spider-Verse (2023), it turns out Norma gave Spinstress's mother the magic artifact that turned her evil and insane in the first place, so Petra would be desperate enough to summon her and allow her to recover the artifact for her own ends. And then there's the little matter of the fine print...
Squadron Supreme: Invoked by name when Tom Thumb tries to get a cancer cure from the Scarlet Centurion, a Conqueror from the Future. The Centurion only offers it if Thumb will help kill his teammate. Thumb refuses, but it turns out the cancer cure is meaningless for 20th century people anyway, thanks to people in the future having better health. And the Scarlet Centurion knew all this anyway. He just wanted to be a dick.
Thunderbolts: In Thunderbolts (2012), the Leader negotiates a contract with Mephisto on behalf of the team. The Leader is cunning enough to work out a deal that is favorable for the team. At the end of the run, when the Leader is trapped by Ghost Rider's Penance Stare by the rest of the team as punishment for all of the crap he's pulled, Mephisto shows up with to "renegotiate".
The Defenders made a deal with Loki to have powers, and become his pawns against the Ultimates.
Ultimate Avengers 3 deals with Ghost Rider, which naturally involves this. Many years ago, newly-wed couple Johnny Blaze and his girlfriend Roxanne were sacrificed by a biker gang to the Devil in exchange for political power. The Devil, being the Devil, decided to give Johnny an offer: Resurrect him as his agent in exchange for Roxanne's life, then sends the Rider after the biker gang in an Attempt to Collect. Then he empowers the last man standing as another Ghost Rider for his own amusement.
Fear Itself: Cyclops sent Illyana, Shadowcat and Colossus to Cytorak in the hopes of getting the Juggernaut depowered a little. It worked, though Piotr took his sister's place and became the new Juggernaut. Illyana knew he would do this, and allowed it just to show Piotr that demonic corruption changes people forever. Worse, she could have freed him at any time with her own powers but let him suffer just to make her point.
X-23 (Laura Kinney) combines this with a variation of Chess with Death in the first arc of her Liu series. Throughout the story Hellverine, a demon using Wolverine as a Meat Puppet, is attempting to seduce Laura into his service as leader of his armies (and possibly just plain attempting to seduce her). He argues that her refusal is pointless because she already belongs to him as a result of being a clone (who he claims don't have souls), and because of all the blood on her hands. Laura continues to resist him, eventually culminating with Hellverine attacking her (sort of) boyfriend, Hellion. He then offers to spare him if Laura agrees to serve him. Instead she makes a bargain: If she can prove his assertions about her wrong, he'll leave her alone and restore Julian. Commence a Battle in the Center of the Mind where Laura revisits her past traumas and, with the help of the Enigma Force, comes to terms with the fact that she wasn't born evil and was herself a victim. Thus winning the contest and saving both herself and Hellion.
She later enters into a bit more of a conventional one during Circle Of Four, in which Mephisto offers to restore her, Red Hulk, Ghost Rider, and Venom to life after they've been killed by Blackheart, in exchange for stopping his machinations to unleash hell on earth. They succeed and Blackheart is defeated, and all four are revived as Mephisto agreed. Unfortunately, they also owe him another favor at a later date, the terms of which have yet to be revealed...
All-New Wolverine #6 reveals her clone "sisters" made one with Kimura to help them escape from Alchemax Genetics. Bellona elected to be the one to pay the price to ensure Gabby walked away free, but it's yet to be revealed just what that price is.
X-Force: Sunspot makes a deal with Selene, an immortal sorceress, and Blackheart, the son of Mephisto, to reincarnate Sunspot's dead girlfriend in exchange for him serving under Selene at her villainous Hellfire Club. Juliana is brought back from the dead and Sunspot's involvement with the Hellfire Club becomes an Aborted Arc that he doesn't have to follow through, so he comes out pretty well at the top.
