WARNING: In many cases, the very fact that this trope applies to a work serves as a spoiler. Proceed at your own risk.
Protagonists becoming increasingly villainous in Video Games.
- Assassin's Creed Rogue details the journey of Colonial Assassin initiate Shay Patrick Cormac from a member of that order to becoming disillusioned with it after attempting to reclaim a Precursor artifact causes a massive earthquake that devastates the city of Lisbon and leaving it rather violently, ending up a member of the Templars, becoming responsible for the devastated state of the Assassin Brotherhood at the beginning of III and killing Adewale from Black Flag.
- Battle for Wesnoth: In the aptly titled Descent Into Darkness campaign, the protagonist is an apprentice mage who starts to delve into black magic to protect his hometown from raiders. At the start, he's learned to summon basic zombies, the use of which gets him rejected by his hometown. By the end of it, he's wiped out the raiders, but he's also become one of the most powerful liches Wesnoth has ever seen and spends his centuries killing off heroes who had thought to slay an infamous lich lord.
- Borderlands:
- This is pretty much the context for Borderlands: The Pre-Sequel!. Here, Handsome Jack, previous Big Bad of Borderlands 2, is shown as a small-time Hyperion manager trying to save millions of lives from Zarpedon. At one point he even laments that innocent people are suffering because of Hyperion's war with Dahl's Lost Legion, stating that having problems with Hyperion is one thing, but the people on the moon don't deserve to suffer. The player gets to watch Jack slowly descend into the amoral, self-centered, enormously unethical and downright villainous behavior that we get to see by the time of Borderlands 2.
- Unlike most cases, though, it's ambiguous if Jack is becoming a worse person, or just taking advantage of the situation to get enough power that he doesn't need to hide who he is anymore. There's also the fact that at this stage he has already enslaved his own daughter, used the remains of a dimensional beast to secretly create a Wave-Motion Gun and pretty much kickstarted all of this to claim the contents of a Vault for himself alone.
- Borderlands 3 confirms that he was always an asshole (because of his grandmother's abuse), but he used to be a high-functioning asshole and a loving father, until his life was ruined when a bandit kidnapped his daughter, and when she used her powers in self defense, she accidentally burned her (mute) mother to death. From there, it kind of snowballed as Jack kept his daughter imprisoned so she couldn't turn siren-psycho, only to eventually turn psycho himself. For extra ambiguity, it turns out that Tyreen's father did the opposite of what Handsome Jack did to Angel, teaching her about all the fun vault-hunting adventures she would have with her powers once she became an adult. That didn't turn out well.
- In Castlevania: Lords of Shadow, Gabriel goes from being a holy warrior to Dracula himself.
- Cry of Fear does a twist on this trope, where it's revealed that the Simon you're playing as is a projection of himself in his therapy journal. Depending on the ending this either applies to the real Simon (who kills the girl he has a crush on and/or his therapist and then himself in the bad endings) or Book Simon (who becomes a bloody monster like the ones fought throughout the game and has to be defeated for Simon to start truly healing his mental health in the good ending).
- Dark Souls: The Dark Lord Ending is treated like this by Kingseeker Frampt (and presumably Gwyndolin). The truth is... more complicated.
- Frampt claims this before the fact, but after the Dark Lord ending he bows to the player and greets them as the new Dark Lord along with the other Primordial Serpents, suggesting that he either changed his mind or was lying the whole time.
- Edna & Harvey: Harvey’s New Eyes can be considered this if you have Lilli stab Dr. Marcel in the ending. (The narration phrases it in terms of her becoming The Unfettered, but notes that she did in fact just kill a worn-out old man who was completely helpless and at her mercy.)
- Fallen Hero has you play as the former hero Sidestep, who's on their inexorable way to a villainous career, but just how far you fall is entirely up to you.
- The Lone Wanderer's story in Fallout 3 can become this.
- Ditto for The Courier in Fallout: New Vegas. You might start out as someone helping communities and stopping raiders. But when you get dragged into the main plot, some paths will require you to take awful actions, like betrayal and mass murder to proceed.
- Basically, the whole point of Far Cry 3. In the end, it's up to you to decide whether Jason Brody is redeemable or not; - in almost comical defiance of the quote on the main page, if he chooses to stay on the island and embraces its warrior-culture, he dies a villain. However, if he chooses to leave with his friends, he lives as an incredibly traumatized yet redeemable hero.
- An interesting example happens in Harvester. While Steve has the option of going around and killing the entire town, the ending reveals that the entire town of Harvester is a literal Murder Simulator trying to turn Steve into a Serial Killer. The player has the option of playing this trope straight or defy it.
- Heroes of Might and Magic's first Heroes' Chronicles campaign details the rise and fall of Tarnum, a barbarian whose only goal is to free his people from the tyrannical rule of the Bracadan wizards to re-establish the glorious barbarian empire of old. Throughout the campaign, various events cause him to grow more paranoid and ruthless, with the tipping point being his poisoning of all his generals, whom he suspected of treachery. He is eventually ended by King Rion Gryphonheart, the first Erathian king, in a Combat by Champion. The remaining campaigns detail his redemption after he is not admitted to the barbarian afterlife. His final redemption comes in the barbarian campaign of Heroes of Might and Magic IV, where he guides a young barbarian named Waerjak in uniting the scattered tribes in a story mirroring his own, minus this trope.
- Taking the non-canon path in both Knights of the Old Republic games will be this for the PC.
- As with the Knights of the Old Republic example above, taking the Dark Side paths in the Dark Forces Saga games Jedi Knight: Dark Forces II and Jedi Knight: Jedi Academy will turn the games' storylines into this for their respective player characters. This is particularly true of Jedi Knight, where Kyle's descent into darkness is determined by the totality of the player's actions throughout the game - slaughtering noncombatants, delving too much into Dark Side powers, etc. - whereas Jedi Academy presents players with a single, discrete choice to go light or dark.
- In Live A Live, the penultimate chapter turns out to be a condensed version to fit with the "short story anthology" nature of the game's plot structure. As it turns out, it's actually detailing the Big Bad's Start of Darkness and tying all the previous, heretofore seemingly-unrelated short stories together. The chapter's focal character is Oersted, once a hero to his kingdom. Oersted is tricked into killing the king, which sees him branded a traitor and outcast, and he's even believed by many to be the demon king. To make matters worse, it's revealed that his best friend, Streibough, orchestrated the whole ordeal to get revenge for Oersted always delegating him second-fiddle. To top things off, after having been betrayed by his former friend and adventuring companion, Princess Alethea, the woman he was in love with, was Driven to Suicide by Streibough's death at Oersted's hand, having fallen in love with him instead. After losing everyone and everything dear to him, Oersted says that, if people already believe him to be the Lord of Dark, he might as well be one, and so he becomes the Lord of Dark, Odio.
- The Metal Gear prequel games - Snake Eater, Portable Ops, Peace Walker, Ground Zeroes and The Phantom Pain - are this for Naked Snake/Big Boss. Snake Eater kicks off his Start of Darkness when he is forced to kill his old mentor/Parental Substitute, the Boss, as part of a Government Conspiracy, and The Phantom Pain, taking place ten years before the original Metal Gear, completes his fall by making him a revenge-driven, self-confessed "demon."
- Phantom Pain alone is fueled on this trope as a figurative interpretation of one of the more canonical story interpretations. The game has a hidden "point" system where the player is assessed as more evil for doing certain deeds, some of which are crucial to the plot. But if a player goes all in, the shrapnel in Snake's head becomes a devil horn, and he becomes permanently stained in the red blood of allies he has betrayed and enemies he has needlessly killed.note By the end of the game, Snake looks in the mirror, and disgusted by what he sees, shatters it. As he walks away, turning his back on the man he once was, his organization's emblem on his shoulder has changed from the Diamond Dogs one he had throughout the game, to the Outer Heaven one from the game in which he is the villain.
- This trope applies to both Nier and NieR: Automata. In the first, Nier only sees the shades as mindless killing machines, and he's right at first, about the ones near his village that were exiled for their violent degeneration. Then he invades a shade stronghold to find his daughter/sister, and the peaceful shades, unable to communicate, are forced to defend themselves when he assumes they are a threat. This cycle of assumption and revenge escalates until he has committed genocide against the shades and killed a living Cosmic Keystone, dooming both shades and "humans" to extinction. In Automata 9S passes the Despair Event Horizon after realizing that the Machine War is not only pointless but that Yorha was created to keep the war going and then be disposed of. Grief-stricken after the death of 2B, he decides to get revenge on A2 and destroy humanity's remaining data to "solve everything".
- In Ravenmark: Scourge of Estellion, Livia Cassianus is a good person trying to serve her country. Over the course of the campaign, she falls in love and grows to accept her new role as the Unexpected Successor. However, her lover's Heroic Sacrifice at the end drives her over the edge, resulting in Livia becoming the ruthless Scarlet Empress by the time the sequel rolls around, in large part responsible for the sorry state of the Empire.
- In Shin Megami Tensei III: Nocturne, the entire game can serve as this to the Player Character depending on what ending you choose.
- In Spec Ops: The Line this happens to both Col. John Konrad and Capt. Martin Walker. They both came to Dubai hoping to help but Konrad and his 33rd battalion ended up committing ever greater atrocities on the inhabitants of Dubai under the pretense of maintaining order while they evacuate the city, which eventually led Konrad to commit suicide once he realized what he had done. Walker and his Delta squad came to look for the remnants of the 33rd but ended up killing every single one of them and most of the locals. In two of the endings, the events of the game have driven Walker so deep into insanity that he either massacres the US army rescue party that came looking for him or dies trying in the attempt. In another, he has a belated Heel Realization and kills himself just like Konrad. Or Walker can have that belated Heel Realization... then defy the trope in another ending and decide to live and go home, facing and attempting to pay for his crimes even at cost of becoming a broken Shell-Shocked Veteran.
- Stranger of Paradise: Final Fantasy Origin is this for Jack Garland, a "Stranger" sent by the Lufenians to enforce order in the world of Final Fantasy. Upon realizing the harm the Lufenians inflict on the world for the sake of their experimentations, he, along with his allies and the Dark Elf Astos, concocts a plan wherein he would be ultimately Driven to Villainy, in so doing becoming an avatar of "Chaos" that would sever the world from the Lufenians, then become the villain whose defeat would ultimately save the world from darkness. In short, this game is the Origin Story for the main villain of FFI, Garland/Chaos.
- Sarah Kerrigan's plot-arc from Starcraft could basically be described as "heroic moral center" to "Brainwashed and Crazy Dragon" to "Big Bad in her own right". But by the time of Amon's war, she comes back around to a heroine once more, strong enough to kill the God of Evil.
- Tales of Destiny: Leon's Side in the remake is Leon's journey from cold-hearted Anti-Hero into Defrosting Ice King, into forced villainy and death.
- Jin Kazama in Tekken 6. Regardless of his reasons for doing it, he plunged the entire world into war and nearly cruelly executed his uncle (it's not like he wasn't enjoying it) based on selfishness and a theory. Jin himself recognizes what his actions have turned him into, even though he's the only one who could have done what he did.
- Terra Invicta: Commissioner Kiran Banerjee of the Protectorate gradually goes from a wise and well-meaning humanitarian to a cynical, human-loathing Quisling who finishes his story by obliterating the United Nations (as well as a big chunk of New York City), the same peacekeeping organization he served faithfully for decades, to enforce an authoritarian nanny state which is wholly subservient to the alien invaders.
- Jack Boyd from the This Is the Police series is one of the most severe cases of this. In the first game, he's governmentally corrupt, but still morally sound in trying to do the right thing and make a solid living by the end of his tenure, even if he's unable to due to his superiors screwing him over at every turn. Between being forced to work with the mafia, to Robespierre leaking out potentially doctored files detailing supposed wrongdoings of Jack, to Mayor Rogers firing Jack despite saying he wouldn't, Jack is left with absolutely nothing by the end of the first game, leading to him abandoning Freeburg and fleeing to Sharpwood in the sequel. After fending off an assailant, he's taken into custody and strikes up a deal with Sheriff Lilly to help her run the department, and because she's an Extreme Doormat who has a hard time running the department, Jack uses this opportunity to explain that he's free to do whatever he wants because Lilly's helpless without him. After a scuffle for position of co-sheriff with Britt Carter, a plan instigated by Liam Henderson to get Jack killed, and Jack's old colleague Lana telling him to turn himself in, Jack hits the Despair Event Horizon, leading to his soul being fully corrupted by Forest Spirits. Once he's gone from a Jerk with a Heart of Gold to a full-blown Corrupt Cop, he ends up crossing the Moral Event Horizon by killing everyone who ever knew his real identity; even ones who supported Jack to the end, such as Emma and Moreno.
- Total War: Warhammer III has Prince Yuri Barkov of Kislev, who you play as in the tutorial campaign. At first a heroic and beloved prince of Kislev, he sets out to learn why the bear god Ursun hasn't ended Kislev's winter with his roar. In the course of his campaigns, he learns it's because the Daemons have captured and are slowly killing Ursun, and sets out to free him, in the process however, he starts to take more callous and cruel actions, as well as becoming more vicious and abrasive towards his men in pursuit of his goal. By the end of the final tutorial mission, Yuri has turned into a vicious monster himself who doesn't hesitant to kill his own beloved brother and offer his skull to a Daemon of Khorne to bridge the way to Ursun's prison, and when confronted with the bound Ursun, he's so far gone that Bela'kor's words convince him Ursun is to blame for all of his misfortune and he shoots Ursun with a chaos-tainted bullet, mortally wounding him. After doing that and being blasted away by Ursun in retaliation, the dying Yuri calls out to the chaos gods for more power and they grant it to him, transforming him into the Chaos Undivided champion known by his title of God-Slayer.
- The alliance campaign of Warcraft III does this with prince Arthas and the Trauma Conga Line that leads to him becoming The Lich King.
- To a lesser degree, we have Illidan, Sylvanas, Maiev Shadowsong, Kael, and Grom Hellscream, though admittedly several of these became Anti Villains while Grom redeemed himself via Heroic Sacrifice. Really, it would be easier to list the Warcraft characters that don't follow this route.
- In World of Warcraft, Grom's son Garrosh began as a seemingly good-natured Orc, tormented by the sins of his father. As his personal story continued he became increasingly brutal and veered further into General Ripper territory, culminating with his being the end boss of an entire expansion pack following a pogrom against all non-Orcs and his attempts to steal the power of the Sha.
