Common sense says to avoid deals with shifty individuals. If characters sends out red flags, then it's best not to bind oneself to them through a bargain. Sadly, some people don't have that sense.
Game characters are often guilty of this. Several have made deals with the Devil. This can either be the actual Satan or some other overarching force of malevolence. These bargains usually help facilitate the adventure, but it comes at a cost. Not only does it place the character's soul at risk, but it makes them seem phenomenally stupid.
7 Kratos - God Of War
Kratos has always taken pride in being a Spartan warrior. As a young man, though, this inflates his ego beyond belief. He's so successful as a general that he grows drunk on his own victory and unwilling to let it fizzle out.
Such is the case when he's overpowered by the barbarian hordes. Before meeting a killing blow, Kratos calls on Ares--the God of War--for aid. The evil deity saves his life and grants him more power, but he demands eternal servitude from the Spartan. Kratos pays this price but descends further into his homicidal madness. This inadvertently results in his family's death, setting in motion a lifetime of misery, revenge, and regret.
6 Hat Kid - A Hat In Time
This girl of few words accommodates most denizens of this wacky world, but that kindly nature sometimes works against her. The worst instance is when she gets to Subcon Forest, where she meets the screaming shadow known as the "Snatcher." He's as blatant as bad guys come, and he threatens her with death until she signs a contract. This requires her to complete dangerous errands around the spooky woods. Ultimately, his threats prove hollow. He attacks her anyway, resulting in his sound defeat. One would think that would be the end of his hijinks.
Sadly, Hat Kid makes the same mistake in the DLC with Death Wish Mode. Here, the Snatcher ropes the plucky protagonist into over a hundred challenges specifically designed to kill her. If that happens, he takes her soul. She should really stop indulging this guy, especially with such deadly stakes.
5 The Velen Peasantry - The Witcher 3: Wild Hunt
It's generally best not to judge a book by its cover, but these "Ladies" of the Wood put that to the test. Many peasants in The Witcher 3 have little faith in nature or their own ability to survive. As such, they place themselves under a high power. That power is a trio of witches in Crookback Bog, who promise protection and ample harvests to their followers. This is why Velen's villagers make regularly sacrifices to them. These are often morbid offerings, such as severed ears. That should have been the first red flag.
These Crones are horrific, sadistic creatures who regularly feast on human flesh. That's clear from not only the sacrifices they demand, but also their reputation for kidnapping children. These factors make the Crones worse than most dangers in Velen, so their "favors" aren't remotely worth the asking price.
4 Riku - Kingdom Hearts
Despite being arguably the most complex character in the Kingdom Hearts series, Riku has an annoying chip on his shoulder in the first entry. He always strives to do things his way and beat his best friend, Sora, at whatever game they play. This fuels his allegiance with Maleficent and the other Disney villains, as he believes Sora is getting too caught up in self-righteous heroics to remember who his real friends are.
When the mythical Keyblade abandons Riku in lieu of Sora, the angry teen meets a mysterious figure named Ansem. He offers to help the kid realize his full potential through darkness. Aside from the obvious mistake of talking to a creepy cloaked figure, this demonstrates a failure to learn from one's mistakes. Predictably, the deal goes south, as it's really a plot to possess Riku's body and use him to unlock Kingdom Hearts. At least the little idiot atones for his sins in later games.
3 Qwark - Ratchet & Clank
No one considers this clown a pillar of intelligence, but his actions in the first Ratchet & Clank border on baffling tunnel vision. Qwark is a superhero obsessed with his own brand. He signs a contract with Chairman Drek to promote that brand, but he should have read the fine print.
The joke is how obvious Drek is as an evil businessman. That's clear from his thinly-veiled video ads for his real estate venture: destroying planets, taking chunks from those planets, and piecing them together into a new one. Anyone who'd do that would have no qualms about breaking promises. Not to mention, Qwark's public affiliation with Drek goes against whatever heroic reputation he accumulated. As such, it irrevocably taints the brand that he cares so much about.
2 The Illusive Man - Mass Effect 3
With so many alien species looking down on Earth in Mass Effect, it's understandable to want a strong presence for humanity. The Illusive Man's method of doing so, though, needs work. In the trilogy's final chapter, he allies himself with the Reapers, thinking that he can manipulate and control them. Such an assumption is pitifully shortsighted, and it only takes a quick glance at the Reapers' history to realize that.
These are artificially intelligent machines which have been around for millennia. That means they have thousands of years' worth of knowledge compared to the Illusive Man's single lifetime of scheming. It also means they've defeated more enemies of greater repute, such as the Protheans. Finally, they're bent on the extermination of organic life. The Illusive Man falls into that category. He should be working with the Shepard and the other heroes, but he repeatedly undermines their efforts. This all but guarantees galactic destruction. Only the most narrow-minded narcissist would think this turns out well.
1 Cuphead & Mugman - Cuphead
The deal is with the literal Devil in this case. Cuphead and his brother, Mugman, play a game of Craps against him. What possessed them to do this is a mystery, but the Devil defeats them and is ready to deal out their demise. Desperate to live, the brothers agree to do their opponent a favor. Little do they know that they'll soon wish for death.
Cuphead and Mugman must track down the Devil's other debtors. This leads to the main adventure. Theoretically, it's better to risk their lives than resign themselves to doom, but these battles are among the most brutally difficult in recent years. As a result, players likely lament the brothers' stupidity.