In The Awakened Fate Ultimatum, if you choose to have Shin not try to save Eri after she is kidnapped by devils, he receives a package containing her severed head. This causes him to go full monster, killing everyone around him, destroying Celestia, and then the devils that come to investigate the carnage. You are then dumped to the game's title screen.
Elizabeth crosses it in BioShock Infinitein the Bad Future that results from her being recaptured by Songbird. In Comstock's attempts to get her to take up his mantle, she is tortured both physically and mentally, but holds on to hope that Booker will rescue her. However, he doesn't, and Elizabeth is convinced that he abandoned her; in reality he was stopped and probably killed by Songbird. With nothing left to hope for, she goes full on Woobie, Destroyer of Worlds and accepts the role of Comstock's successor, sending Columbia into war-preparations and subjecting any dissenters to a Mind Rape that transforms them into easily manipulated lunatics. And when she realizes why Booker didn't save her, all her attempts to try and stop the monsters she's created fail. It's only through the intervention of the Luteces that she can find the will to prevent this future from ever occurring with the help of another version of Booker, and even when this plan comes to fruition, Elizabeth still can't see any hope for herself.
Blank Dream has the final memory Mishiro needs to recover, which is her only friend and the only person she feels cares for her, Ayato, throwing her out of the way of a speeding car but getting hit himself, and dying right in front of her. The narration mentions her heart "dying in that instant", and that was the final straw that pushed her to throw herself into Mirror Lake. Worse, in two of the endings, Mishiro finds out that the person behind the wheel was Ayato's mother, and she was aiming for Mishiro.
(I... need to save... Tsubaki... but... I feel like I... like I don't... have... anything...)
Terumi feeds on others' despair to survive. He happens to be very good at causing this to extraordinary levels in almost everyone, and does exactly that, even if it's just for his own amusement. Every single ending, except his own, ultimately is a Heads I Win, Tails You Lose situation for the character. He uses his abilities to turn Noel, the girl who is loyal to him and falsely believes him to be a force of good, into a sobbing wreck of self-loathing and hatred. His Motive Rant, which is delivered after said Heads I Win, Tails You Lose situation, sums up that he thinks that everyone who have crossed the Despair Event Horizon are the only honest people, everything else is lies, those who believe them are liars, and he's willing to make his own brand of truth of "Everyone, cross the Despair Event Horizon" to become the accepted truth in the world.
Ryu's Despair Event Horizon occurs when the summoners of Chek (who all appear to be children) are massacred in front of him by Rasso. Ryu ends up having a Heroic BSoD which releases the Kaiser Dragon — a kaiju-esque dragon that is a Physical God — and results in him going into an Unstoppable Rage until receiving a Cool Down Hug from Nina.
This is also after no less than two previous attempts by The Empire to kill Fou-lu. Who is a literalGod-Emperor. Whom the Vestigial Empire predecessors of The Empireexplicitly summoned there 600 years previously (botching the summoning and leaving the Physical God they were trying to pull across in two separate bodies separated by 600 years on opposite sides of the world) to unite their people and bring peace. And the main person trying to kill him, Yohm, is also explicitly a priest who knows damn well who and what Fou-lu is but is trying to kill him anyways.
In Castlevania: Lords of Shadow, Gabriel crosses it right after a moment of utter triumph when he kicks Satan's ass when he sees that Marie is about to leave for the afterlife forever and that he cannot go with her. Realizing that the hope he believed in was hollow, Gabriel collapses and cries silently. Even centuries later, he has not recovered. As the immortal Dracula, all he does is hide in shadows while longing for a death that may never come.
Schala Zeal of Chrono Trigger is left so broken in sadness and despair that she willingly resigns to her fate of being trapped in the Dream Devourer. Not even her brother's will to save her lifts her spirits; in fact, his lust for power to that end only makes it worse.
This is the goal of Junko Enoshima from Danganronpa. She wants to drive the world to madness-inducing despair in order to break the boring status quo that she believes hope brings.
In Dante's Inferno, Dante's will is steadily broken as he goes deeper in Hell and is forced to face the many sins he committed in life. When a corrupted Beatrice calls him out on his misdeeds and betrayal of her trust, he falls to his knees and gives up on trying to redeem himself, deciding that he deserves to be trapped in Hell.
Darkest Dungeon: Heroes afflicted by Hopelessness will cross this one and practically give up on leaving the dungeon alive. They will spend turns weeping and lamenting their own fates and those of their unfortunate partners, curse their luck, and even try to kill themselves, stressing everyone else out.
Ancestor: There can be no hope in this hell. No hope at all.
In the Dark Souls series, losing their sense of purpose in life and crossing the Despair Event Horizon is the moment an Undead will fully turn into a mindless (and violent) Hollow. And considering the overall tone of the series, this is bound to happen sooner or later. Moreover, many of the boss and NPC characters incorporate this trope into their lore. Examples include:
The Crestfallen Warrior from the first game, who gave up on his quest and just sits on Firelink Shrine acting as a Deadpan Snarker to the player.
King Vendrick from the second game, who's built up as a Disc-One Final Boss until you meet him and see that he has hollowed completely in the crypt. Meeting his sane self within his memories gives you dialogue where he says that he doesn't see himself fit to be a king as much as he sees himself as fit to be a jester. Ouch.
According to item descriptions, Yohrm The Giant from Dark Souls III protected the capital city he ruled over with a tower shield and a machete in hand, until he "lost the one he wished to protect" and discarded his shield, taking to fighting as a berserker with nothing left to lose, before he decided to be done with it and sacrifice himself to link the first flame. When he's brought back from the dead along with the other lords to link the flame again, it's implied that he crosses the horizon a second time once he sees the state of both the world and his old kingdom.
Keisuke, already destabilized by a whole childhood of witnessing and suffering bullying, finally snaps when he sees Midori being nearly lynched to death by the people she was trying to save. He spends the following days going Knight Templar and killing anyone that commits any kind of injustice.
Yasuyuki Honda crosses this in the Escape ending. He spends the whole week trying to escape the lockdown so he can see his hospitalized son, only to discover that he's too late, and because they broke through the blockade, the whole world's gone to hell. This sends him completely over the edge, and he calls out the "heroes" responsible in a nightmarishly backwards way, complete with Slasher Smile.
Material released after the first game reveals that Prince Aidan aka The Warrior went over this when he discovered that in killing Diablo, he killed his baby brother Albrecht, and saving Albrecht had been his driving goal. This may have driven him to jam Diablo's Soulstone into his forehead, an action that he probably would not have done otherwise.
At the beginning of Act IV, everyone in Bastion's Keep who isn't dead following Leah's death and Diablo's resurrection as the Prime Evil at the end of Act III comes damned close to crossing this. Haedrig, the blacksmith who's followed you faithfully throughout the game, comes probably the closest to it:
Haedrig: I thought I could make my wife's death mean something. It doesn't matter now, does it? Player: It does matter. You are here now, and we might still turn the tide of this battle. Haedrig: Right. I'm sure that's a comfort for Leah now that she's gone too. I've been a fool. You don't get to make things right. This world isn't made for redemption.
In addition, the angels of the High Heavens have also fallen to despair as a result of Rakanoth capturing Auriel, the Archangel of Hope. Only by killing Rakanoth and freeing her do you restore hope to both the angels and everyone else.
Before Digital Devil Saga starts, Angel crossed this when her boyfriend died in her arms from injuries sustained in a terrorist attack on his hospital, all due to fear of the new, possibly not even infectious disease she'd been working on finding a cure for.
The player can push Fenris over the Despair Event Horizon by agreeing to give him back to the blood mage who had previously enslaved him. He's so gutted by the betrayal that he doesn't even get angry, just bows his head and leaves with the slaver without a fight.
Implied with Orsino at the end of the game. Seeing his fellow mages cut down one by one with no hope of surrender, he finally gives in and uses blood magic in a Taking You with Me type deal. If you're on the side massacring the mages, he's downright Laughing Mad as he gives in. If you're helping the mages, the casualties are still too much for him. "Why don't they just drown us as infants? Why wait?"
The eponymous protagonist gets hit with this hard at the end of the first half of the game when he completely fails to save his sister (Replicant version) or daughter (Gestalt release) from the Shadowlord and is forced to sacrifice one of the only true friends he's ever had for a hollow victory against a Shade. This destroys the bubble of hopes and dreams he was trying to create for him and his surviving family member and turns him into an embittered and murderous Blood Knight who revels in killing Shades as an outlet for his anger and despair as he tries to get back what he lost.
Pascal hits this very hard when, after he and A2 fend off invading machines to protect the child machines under Pascal's care, they discover that the children took their own lives. With every member of his village now dead, Pascal loses the will to live and asks A2 to end his suffering, either by killing him or erasing his memories.
Dwarf Fortress has this as a fundamental aspect of managing your dwarves. They can become unhappy through a variety of reasons from simply not having any alcohol to drink through to the deaths of close friends or family. Getting a dwarf depressed enough will push them over the edge and cause them to lose their sanity. Depending on several factors this can be anything from a minor nuisance to extremely dangerousTo be specific... Depending on the dwarf's personality, they can either tear off their clothes and run all around the fortress babbling madly; simply stop responding to the world and stare off into space for the rest of their now-short lives; commit suicide through water, magma, or starvation; or try to kill everything that moves. If you're lucky, events can contrive to make this game-ending depending on your fortress design and how close other dwarves are to being over the edge themselves. Indeed, events can (or more usually, do) spiral out of control until your entire fortress is over the Despair Event Horizon.
This is the most common reason to call upon the Frenzied Flame. The reason it has a foothold in the setting is because a tribe of nomadic merchants were accused of worshipping it (despite probably being innocent) and all buried alive because of it, causing them to "chant a curse of despair" and actually summon the Frenzied Flame.
This is a possible ending of Millicent's questline, as at the end, Sage Gowry will ask you to betray Millicent so she can succumb to the Scarlet Rot within her and "flower" into a Scarlet Rot monster. You do not have to do this; if you instead fight alongside her, she will retain her sanity and instead decide to die as herself, leaving you an important plot item.
It's implied that Vyke and Bernahl went through this back when they went on the same quest as you. The thing that pushed them over the edge was the fact that their Finger Maiden would have to make a Heroic Sacrifice to open the way into the Erdtree, pushing them to abandon their quests. Vyke turned to the Frenzied Flame (only to fail that too), and Bernahl joined the Volcano Manor.
Sir Gideon Ofnir, the leader of Roundtable Hold, will go through this after you open the Erdtree, as whatever he discovered pushed him to believe that the mission of the Tarnished was impossible and the ultimate plan for them coming to the Lands Between was just to fight each other and everyone around them forever in a futile attempt to become a Lord. He then turns into a boss fight.
The Elder Scrolls IV: Oblivion has Agronak gro-Malog, the Orcish Grand Champion of the Arena. His father was a noble, and he asks the player to help him find the truth of his heritage. After the player reveals to him that his father was a vampire, he believes himself to be a monster and doesn't even fight back when the player fights him in the Arena.
In Fallout, it is possible to send the Master over the Despair Event Horizon by convincing him that his plan to conquer humanity with his Super Mutants is doomed to failure.
The Master: But it cannot be! This would mean that all my work has been for nothing! Everything that I've tried to...a failure! It can't be! Be! Be! Be...I...don't think that I can continue. Continue? To have done the things I have done...in the name of progress and healing...It was madness. I can see it now, madness. Madness? There is no hope. Leave now. Leave...while you still have hope...
After spending a year in coma and seeing the destruction of the world firsthand, Cid's death proves to be Celes's final straw, driving her to toss herself off a cliff. She survives by a miracle, and seeing Locke's bandanna tied around a pigeon's wing gives her a new reason to live.This event can be prevented by successfully playing a minigame, but the path of failure is much better written.note The developers seem to think so too, because the "right thing" to do is willfully obscure and partially luck-based and the remainder of the plot tacitly assumes that the character is dead.
Strago, believing that Relm is dead, allows himself to be brainwashed by the Cult of Kefka, although he snaps out of it once he sees that Relm is alive.
Terra completely gives up fighting thanks to her losing to Humbaba, and it takes her second encounter to be encouraged to fight.
Mog, after thinking that the party has died, just stares at the wall in the Narshe cave, and it takes the party encountering him to see otherwise.
Setzer, after losing his beloved airship, is found drinking at the bar in Kohlingen, and it takes a Rousing Speech from Celes to bring him around.
This is Seymour's motive. After a fairly crappy childhood he hits the horizon when his mother (the only person who ever loved him) sacrifices her own life to give him the power to defeat Sin. His despair drives him to plot the destruction of all life in Spira because he sees it as the only way to bring an end to all suffering.
It also turns out to be the motive for why Yu Yevon originally created Sin a thousand years ago. Seeing that his beloved city of Zanarkand would be destroyed, he transformed his own subjects into one massive Fayth to create an eternal Dream Zanarkand, as well as an all-powerful destructive force (Sin) to provide the power needed to keep Dream Zanarkand alive.
In the sequel Final Fantasy X-2, a Despair Event Horizon is the main motive for its Big Bad, Shuyin, who wants to destroy the world which let him and his beloved die a thousand years ago. To put it in perspective, Shuyin's concentrated despair festered in the cave where he died for a millennium after his death, until it reached a point where the only way he could think to end his pain would be to end the world itself.
Final Fantasy XIII has each of the main characters going over the DEH. Some are more destructive than others.
Lightning, in frustration with PSICOM's persistence in hunting down the L'Cie and Hope's ineptitude, finally goes over the edge. After what could be considered a "The Reason You Suck" Speech, she inadvertently summons her Eidolon, Odin, who wastes absolutely no time in attacking Hope. What gives this example a more literal sense is noting that as long as Hope has health remaining, Odin will always target him first in battle.
Hope has a number of these. The first starts as a mere lack of will to live. Nothing too major. Then, he gets pushed into a state of Tranquil Fury against Snow after the man saves him, believing he didn't save his mother, marking Snow as irresponsible. Needless to say, Hope and Lightning begin to bond due to their mutual dislike of the man, with the latter unintentionally giving Hope the will to create a premeditated murder plan. Just to add to the blunder, she also give him a Survival Knife. This marks the longest in-game grudge, spanning for at least four chapters. Eventually, he comes to a Rage-Breaking Point after fighting a boss, which causes him to explode with anger, blasting Snow off of a roof, leaving him hanging over the edge while Hope attempts to kill him with the same knife given to him. However, this alerts the PSICOM forces looking for them, who blast Hope from the roof. This, however, is passed once the man saves his life. His final, albeit short, one is experienced on the surface of Gran Pulse, where Hope finds that the powerful forces of Pulse are too much for him. He goes on a Heroic Self-Deprecation rant, which unlocks his Eidolon, revealing the truth that Eidolons come when you are on your last legs to display your inner strength to you.
Sazh spends a good bit of his time with Vanille over the deep end. However, he has one of the more memorable ones in the game. After travelling with the girl, soon becoming rather attached to her, Sazh is confronted by Commander Jihl Nabaat, the woman who was to watch over his Cocoon l'Cie-branded son. The woman then reveals that Vanille was the reason Dajh was branded in the first place, and thus the reason he ended up as a crystal, which causes the girl to run in sadness of the revelation and Sazh to go after her in a Roaring Rampage of Revenge. Soon, he succumbs to the sadness of his son's fate, opting to let his then-summoned Eidolon, Brynhildr, kill him. After her defeat, he decides to attempt to commit suicide by pointing his own gun to his temple.
Snow has a large one after the first battle with the penultimate boss, who reveals to the group that Serah's Focus was to destroy Cocoon, instead of saving it. Snow becomes nearly catatonic, with both Vanille and Lightning having to help him out of his rut and restore his faith in Serah. Afterwards, Snow's brand is the farthest along to turning him into a Cie'th, as emotional distress increases the speed of the process. Both of these are lampshaded by Fang.
Vanille suffers a few of them. A famous one is her breakdown once Fang "remembers" everything, exposing Vanille's lies and her Eidolon. This is pushed to a climax after the battle, where Fang motions to knock Vanille a new one... only to stop and hug her, allowing the girl to cry into her shoulder.
Fang suffers two of these in-game. The first is shown when she summons her Eidolon, Bahamut, accidentally after her tirade against the Fantastic Racism Coccon is capable of. Opting to "blast Cocoon out of the sky", she very briefly turns on the group, even drawing her weapon on them. She suffers a much more emotional, but brief, one after her friends are turned into Cie'th by the stress she caused them.
Snow, over Serah's death, spends almost the entire game in one, which results in him becoming a Cie'thin hopes of Lightning killing him. Fortunately, Lightning is able to pull him back from the Horizon.
Noel, due to the aforementioned death of Serah and his role in the death of Etro, suffers from immense guilt, leading to him chasing a prophesy of him killing Lightning in hopes of reuniting with Yeul.
Even Caius Ballad has crossed the DEH. After killing Etro, he no longer has a purpose and longs to die but while some of the incarnations of Yeul wish for his suffering to end, others don't want him to die and revive him each time he does, leaving him unable to die and with no purpose.
Lumina crosses it near the end of the game, as because she is a manifestation of Lightning's emotions that was sealed away after Serah's death, she knows that if Lightning does not accept her, she'll vanish forever.
In the ending, Lightning crosses it when she realizes that sealing herself with Bhunivelze in the Unseen Realm means that she'll never be with her friends again. Then Lumina arrives, and once Lightning accepts her emotions, she's able to call out for help.
The Stormblood expansion of Final Fantasy XIV is about the Player Character trying to pull the people of Ala Mhigo and Doma out of their own DEH and rise up against the Garlean Empire. As for more specific examples:
The Ala Mhigans tend to bounce up and down in this trope, but hit this pretty hard due to The Griffin/Ilberd's mad and suicidal plan to kill his people to create a brand new Primal.
Conrad, leader of the Ala Mhigo Resistance, hits this briefly after the Garleans raid Rhalgr's Reach, leading to the deaths of many people, including the man he wanted to succeed him. He's able to recover after awhile.
The Doman people have been in one due to a failed rebellion that cost them the life of their old leader (and is thought to have cost them his son as well, but he's still alive, waiting for the right time to return) and Yotsuyu's petty retribution.
Yugiri hits this as she rescues a group of Domans, who are now scared shitless of being punished. The Player Character is able to shake her out of it.
Cody Travers from Final Fight and later the Street Fighter series. While it is not actually seen in the games, multiple games tell the story of his downfall, which occur after the ending of the original Final Fight. Cody and his friends go out to save his girlfriend from the Big Bad in Final Fight. On the way, he beats up a corrupt cop named Edi, who later arrests the hero for assault and battery. Next, his girlfriend dumps him and leaves the country to study abroad. Afterwards, he is let out of jail and tries to get revenge by fighting criminals outside. He gets arrested again, and becomes addicted to fighting within prison. He then eventually breaks out, and joins the Street Fighter cast in their tournament(s). After all of these events, he usually claims that he will never be the hero again, and often states that all he has left is fighting (which he often exclaims is pointless).
Prince Hardin of Aurelis, now Emperor Hardin, crossed the horizon when he learned that while Princess Nyna cared for him, she didn't romantically love him and only agreed to marry him for the sake of Archanea. This led him to lock himself in his personal room alone drowning his sorrows in booze, until Gharnef disguised as a merchant offered him the Darksphere and turned him into a megalomaniacal tyrant, setting off the events of Book 2 with Hardin himself as the Big Bad. His last words are pretty much a Final Speech in which he begs Marth for forgiveness and begs him to apologize to Nyna in his stead for having been weak enough to give into the corruption of the Darksphere, finishing with his reaffirmation of his love for Nyna.
Lord Sigurd can hold himself up as well as possible when his wife Dierdre is kidnapped, his father Byron is falsely accused of treason and dies, he himself is accused of treason, and both his sister Ethlyn and her husband/Sigurd's Lancer Quan are murdered. However, the moment he sees that his kidnapped wife was actually mindwiped into marrying Arvis, who once was his sort-of ally, he can only scream in utter horror and betrayal right before Arvis himself burns him to death, and Sigurd's army is decimated shortly afterwards.
Sigurd's old friend and companion Tailtiu doesn't fare much better. In the second part of the game we learn that she crossed the DEH after not only being separated from her son Arthur as she and her daughter Tine were kidnapped back into Freege, but also after being subjected to endless abuse from her sister-in-law Hilda, which finally drove her to sickness and death.
Eyvel once was close to this horizon. So much that whatever happened to her (the Battle of Belhalla) robbed her not only of her husband and children, but of her memories of having ever been Brigid, the lost princess of Jungby and a member of Sigurd's troops. Much to our relief, at the end of the game we learn that some years after the second war of Grannvale, she recovered her memories and reunited with Patty and Febail.
Olwen and Misha also get pretty close to it, once they learn about the horrifying child hunts conducted by the Grannvalian empire. They both pull through it via Heel Face Turns.
The biggest example is King Mordred of Etruria, who completely lost the will to reign and left the government to his advisors (many of them treacherous) after his son and heir, Prince Myrddin, died in an accident. And then this is subverted in the end: Myrddin actually reappears, having survived the ambush that almost killed him, and is reunited with his father, so we know that Mordred ultimately got better.
Zephiel Used to Be a Sweet Kid before he crossed his own Despair Event Horizon as well. Throughout his life he had been trying to please his father, but in vain. But when his father started trying to poison him, not only did he give up trying to please his father, he lost all faith in humanity as well. This is further detailed in The Blazing Blade, where you save him from an assassination attempt orchestrated by said father.
Eliwood and Nils both come dangerously close to crossing this once Eliwood is tricked by Nergal into killing Nils's beloved sister Ninian with Durandal when she is forced into her dragon form by Nergal himself.
Renaultdid cross it several years ago, when his partner and best friend was killed in battle. He was so utterly shattered that he threw himself into battle blindly (and killed Lucius's dad in the process) and collaborated with Nergal in hopes to have his friend revived, among other things. He recovers a part of his sanity, however, and becomes The Atoner in the end.
And then we have Harken, an Ace who was thoroughly broken after being the Sole Survivor of Lord Elbert's decimated crew. We meet him as a powerful enemy whom the Pheraen characters must recruit as soon as possible lest he fights them to the death, and his supports reveal how the horrors he witnessed and the helplessness he felt drove him into becoming an Empty Shell of the man he once was. For worse, some other supports (specifically, with Marcus) heavily imply that he had severe self-esteem and abuse/abandonment issues before the whole Break the Cutie deal.
When we meet Lord Hausen, the old man has crossed the DEH since he has learned that his long-lost daughter (Lyn's mother) is dead, his health is failing more and more (and he's being poisoned), and his brother Lundgren is taunting him endlessly about all of it. He's going to succumb to Death by Despair by that point. But when Lyn reaches for him, he manages to come back.
Prince Lyon never was the most self-assured person, despite his Badass Bookworm status and being the Imperial Prince of Grado. (His weak health didn't help either.) But then his beloved father and idol Emperor Vigarde died of illness, so the poor guy's mental health took a big nosedive.
Lyon's advisor, Knoll actually manages to return from the DEH, having witnessed Lyon's fall into despair and then having been slated for execution. Ephraim and Duessel reach for him in the nick of time, and Knoll decides to join them and do what he can to help save Grado.
In Fire Emblem Fates, the Birthright path has Prince Xander crossing this on screen, as in the middle of his duel with the Avatar he accidentally cuts down his beloved half-sister Elise, who takes a fatal hit meant for the Avatar him/herself, she dies in his arms, and he ends up becoming a Death Seeker as he fights the Avatar to the death. It even reflects in the gameplay: Xander is so guilt-ridden by Elise's death that he will never attack the Avatar unless the Avatar themselves instigates the battle, and even then doesn't do any damage when striking back.
The opening of the first God of War has Kratos say that the gods have abandoned him and he throws himself off a cliff. The rest of the game is spent showing what pushed him over the DEH while he slaughters his way through a Greek mythology textbook.
Dwayne crosses it in Grand Theft Auto IV if you decide to kill him in the mission "The Holland Play". It has been established that Niko is the only person he can rely on, and the closest thing he has to a friend. Realizing that Niko has decided to kill him pushes him past the event horizon. While most of the characters that you execute over the course of the game have to be chased down and cornered, Dwaynejust turns his back and waits for Niko to end him. Thankfully, there is a much better alternative.
If Ethan Mars of Heavy Rain fails to save his son Shaun at the end of the game, he will fall into this, ultimately leading to suicide. It doesn't help things that his other son, Jason, was killed near the beginning of the game.
Hunter, in Darkness, an interactive fiction by Andrew Plotkin, plays this one and plays it hard. An early segment has you crawling, cut and bleeding, through a tight space with hundreds of feet of rock above and miles and miles of rock below. The game assures you repeatedly, even as you struggle ever closer to freedom, that this is it — your final resting place. This is where you die. Your light has flickered out and the invisible narrator insists that you will never leave this place, until finally you tear yourself away from the stone gullet and stumble blindly to freedom.
In Ib, Ib herself suffers this in two of the endings. If you do extremely poorly and then fail the Doll Room event, you get the "Welcome to the World of Guertena" or "A Painting's Demise" endings, in which Garry has been driven insane and Ib, though she tries, is unable to do anything about it. This leads to her collapsing in despair and never getting back up again, despite Mary's attempts to get her to wake up.
In I Miss the Sunrise, a lacertian man named Chac seems to have passed this; he was the lone survivor of a ship that was wrecked by the Shine, and is wracked with survivor guilt. In addition, he lost both his wife and his legs. Turns out that he hasn't quite passed the brink; though it takes a Herculean effort, his sidequest involves bringing him back from the event horizon.
In the backstory to Injustice: Gods Among Us, shown further in its prequel comic, Superman crosses it after he is tricked by the Joker into killing his wife Lois Lane and their unborn child thanks to Kryptonite-laced Fear Gas, and since Lois was hooked to a detonator to a nuclear bomb that went off when her heart stopped beating, Metropolis was destroyed on his account as well. Not only does Superman kill the Joker in revenge, but he is also so consumed by this and his unresolved guilt that he eventually becomes completely disillusioned with conventional superheroics and humanity's warlike and criminal natures and decides to turn the Justice League into a Repressive, but Efficient planetary government, while simultaneously shooting down any attempts to redeem him because he just can't accept that what happened wasn't his fault.
Lily from Kindergarten is constantly bullied by her classmate Cindy. In Cindy's mission, she enlists the protagonist's help to play a cruel prank on Lily by dumping a bucket of blood on her. If you go through with it, Lily will decide that she can't take Cindy's bullying anymore and kill herself by jumping into the Nugget Cave, an extremely deep pit in the sandbox. Fortunately, the game's "Groundhog Day" Loop mechanic means that it doesn't stick.
In The King of Fighters, Leona Heidern has spent years at the border of this after she killed her parents and townspeople under Goenitz's More Than Mind Control, with only a big dose of Trauma-Induced Amnesia and her life as a soldier holding the rest of her sanity. When she actually recovers her memories of this, she almost fully crosses the line and then becomes Orochi Leona. Fortunately, her True Companions Ralf and Clark are there for her, so they manage to bring her back.
King's Quest III explains that King Graham passed this when Rosella (his remaining child) was picked for the annual Human Sacrifice to the dragon plaguing Daventry. This is why it falls to "Gwydion" (aka the lost Prince Alexander) to rescue her and the kingdom.
This is the entire premise behind Knights of the Old Republic II: The Sith Lords, as Revan is revealed to have deliberately subjected his Jedi Knights to brutal, dehumanizing battles until their spirit broke and they turned to the dark side.
Oersted in Live A Live. After being tricked, he finds that everyone has now abandoned him and considers him a demon, his only remaining ally is dragged away to be tortured, and he's blamed for the death of said ally, who expends the last of his power to set Oersted free. And then he finds out that his best friend betrayed him to this fate because he was jealous. Oh, and the "Aesop" which has been so far in the game? "Don't lose hope as long as somebody believes in you". That went well. The last person who he hopes believes in him, the princess? After Oersted duels his traitorous friend and kills him, she asks why he didn't come to rescue her (ouch. He did. Straybow only got there first by faking his death and ruining Oersted's life), declares that she loves said traitor, and kills herself. That's the absolute last straw, the severing of his last tenuous tie to sanity. The result? Demon Odio is (re)born and is bent on destroying humanity.
Tali suffers one if you allow the geth to wipe out the quarians. She throws herself off a cliff, and there is absolutely no way to stop her.
Conversely, Legion suffers this if you choose to let the quarians kill the geth. In fact, Legion decides to try and kill Shepard out of hopeless spite, but Tali shoves a knife in his back and saves Shepard while Legion dies.
Likewise, choosing to sabotage the genophage cure will cause Wrex to withdraw all krogan support from the fight against the Reapers and confront Shepard, which ends about as well as can be expected.
The krogan species as a whole is suffering from this — since their culture has a heavy focus on the idea that Might Makes Right, their defeat in the Krogan Rebellions due to the genophage has led them to view themselves as not even worthy of survival, and as a result they've degenerated into internecine warfare and mercenary work and don't put all that much effort into trying to cure the species-wide stillbirth plague.
Your clone, when Brooks abandons them in the Citadel DLC. If you take the Paragon option and try to save them, they flatly refuse to take your hand and simply... let go of the Normandy's ramp. Hundreds of feet above the Citadel streets.
Gavin Archer, if you took the Paragon choice at the end of the Overlord DLC and then fail to save Grissom Academy. You can also save Grissom Academy but lie about doing so.
Archer: God be with you, Commander Shepard. He was never with me. [gunshot]
Ophilia's sister Lianna from Octopath Traveler comes near to breaking when her father Archbishop Josef falls seriously ill near the time she must depart for the Kindling pilgrimage, so Ophilia decides to take her sister's place so she can stay by her father's side. By the time Ophilia reaches Goldshore, Josef has died, leaving Lianna completely broken and allowing Mattias to successfully manipulate her into helping him gain power from the local God of Evil by promising that he will resurrect her father if she helps him. After Mattias has Lianna initiate the dark ritual and then cruelly reveals that He Lied about resurrecting Josef, Ophilia reminds her sister of the time their father told them to remember those who die so their legacies can live, giving Lianna the strength to stop the ritual and thwart Mattias's Evil Plan.
In Odin Sphere, when Oswald learns that Gwendolyn handed over the ring Titrel, which he'd given to her as a wedding gift, to her father Odin, he takes it to mean that she does not love him and is trapped in their marriage. Given that Oswald had latched onto the possibility that Gwendolyn might love him as his last hope in the world, the thought that she has no feelings for him drives him so far into despair that he lays down his sword and lets the Halja drag him off to the Netherworld. Fortunately for Oswald, he's mistaken about Gwendolyn's feelings, and she promptly dons her battle tutu and storms the Netherworld to get him back.
In OFF, at the end of Zone 2, this happens to The Judge after finding out that his brother was killed by Japhet when he took his real form. If you manage to get to the top of the mall after the zone has been purified, The Judge will be there, meowing sadly, saying that he's calling out for his brother, even though he knows that he's dead, because he can't accept the truth. For the rest of the game he will remain there. Until The Batter kills Hugo and stands before the last switch, at which point he'll arrive to confront him and encourages you, the player, to join him in stopping The Batter's "demented crusade".
The Entity from One Shot has long since crossed this by the time the game starts. When going into the Solstice run, you discover that The Entity is actually The World Machine, the simulation the game takes place in. Before the game started they accidentally corrupted one of the residents in their simulation while messing with the code for the world's environment out of curiosity, causing them to panic. This in turn made it worse as they lost control of the corrupted code, sending them into a downward spiral which led to them crossing this and becoming a Death Seeker, no longer caring about their life and only wanting to protect Niko by any means necessary. By the end of the Solstice run, you help them fix their broken programming and save the world for real, allowing them to finally have their happy ending and be at peace with Niko safe and sound.
Lorraine Maillard hits this hard in the finale of The Park. After spending most of the game being mind raped by the Bogeyman, she finally comes to the realization that Callum getting lost in Atlantic Island Park was all her fault, and spends the last segment of the game tearfully cursing herself for being a horrible mother. And then the Bogeyman forces her to stab her child to death with an icepick. The epilogue features her staring catatonically at nothing, unable to respond to police inquiry and not even reacting to the arrival of a strange man with a bee in a jar. The Secret World reveals that being forcibly implanted with the Bee and being press-ganged into becoming an agent of the Council of Venice only made things a thousand times worse; Lorraine kept committing suicide, but thanks to her Bee-induced immortality, she kept coming back. All she had left in life was a thirty-year quest to end her own immortality, thus paving the way for the events of "The Seven Silences".
This is what motivates Wolf to become a robber in PAYDAY: The Heist. According to his backstory, Wolf lost his job when the economic slump hit, his last client refused to pay him for his work, and he and his family became homeless. It was enough to send Wolf over the edge to the point where he suffered a mental breakdown and started to act out based on famous heist movies.
The game uses this as a gameplay mechanic. Anyone hit with the Despair ailment will skip their turn and lose a chunk of SP. If not cured within two of their actions, they will succumb to the ailment and die on their third action. During flu season (11/13 to 11/15, then 12/8 and 12/9) random enemies in Mementos will be afflicted with this ailment, and The Reaper itself is no exception.
In Orthodox traditions, Despair (or Tristitia in Latin) is considered to be an eighth Deadly Sin, and the major villains of Persona 5 embody the trope. In this instance, Tristitia, or Cavum ("Emptiness"), is represented by Takuto Maruki, who lost his girlfriend to catatonic depression because of a very unfortunate indoor burglary/murder case, reducing her to the state similar to Hikari below. This caused him to awaken to Adam Kadmon's powers, only to shuffle her memories to the point of being unrecognizable. The seizing of his research laboratory funds by Shido only broke him further, and during Christmas Eve, Yaldabaoth's plans distorted his persona and turned him into its meat puppet, in which he overwrites cognition and history himself so all tragedies and meaningless suffering, most notably the Phantom Thieves', never happened or are overwritten, bringing them eternal happiness, stagnating their growth or motivation to move forward, and reviving Mementos to the surface to ensure the world stays this way. It is happiness twisted into literal existential nihilism and nothing more.
Yosukesaurus, the "Outcast Dinosaur" who does not follow his Herbivore Dinosaur Hive MindGirl Posse. When the dinosaurs tried to ostracize Yosukesaurus because he led them to a dead-end clearing, they sent him to dispatch the Persona users with the premise that humans made the book that said that the clearing was a paradise; if he does not, they will ostracize him from the pack. Of course he can't stand it and transforms into a carnivorous dinosaur himself. Apparently, he is actually a cognitive copy of the secondary school Hikari, who was ostracized by her friends for having different opinions on ostracizing a bullied student from their group, and that student jumped ship as well.
The person that sent Hikari into the Nervous Wreck state she's in at the start of the game is, in fact, her father, or more accurately, herself. After her relatives convinced her that Individuality Is Illegal, the Trauma Conga Line made her close herself off in her room so she would no longer have a personality. Her beloved father came in, bought her favorite notebook, and asked her, "Why do you have to be like that like that?" That was actually a genuine concern over her welfare; it's only that the question was asked by all of her tormentors before they flipped out on her, effectively activating her Trauma Button and destroying her from the inside.
Near the end of the game, Enlil, the true identity of Nagi, reveals that the Cinema is not just one Cinema, but a series of Lotus Eater Machines located in her domain in the collective unconsciousness. It's pretty evident that Hikari is not the only person trapped, but numerous people are trapped in her domain as well. All of them simply look lethargic, lack any sort of life force, and are just sunk in their depression. The movies in those theaters are all pure negative emotions masquerading as a documentary, and that definitely won't do them any good. Even though Enlil doesn't directly prevent anyone from leaving and the trapped can technically leave at any time they want, they just don't want to because their thoughts have been thoroughly numbed by the despair. Apparently, these hapless people are a representation of how Hikari actually was before the Persona users arrived. It is not only a Despair Event Horizon for them (and her), it is a Fate Worse than Death and More Than Mind Control.
In Pillars of Eternity, the entire country of Dyrwood is falling into despair thanks to the Hollowborn epidemic. It's pretty hard to keep your hopes up when your kids are born without souls after all.
Kyoji Nanba of Racing Lagoon gets depressed as he's defeated by Sho Akasaki (the player character) and loses his chance to race in the Yokohama GP. He then takes a diablo-tuned car and gets himself killed.
This ends up happening to Ramirez after his mentor figure Galacian is killed. This leads him to bring down the Rains of Destruction and destroy the whole planet instead of conquering it, reasoning that Galacian was the only one who could save the world.
As a bonus, Galacian is killed because one of his subordinates, Belliza, crosses her own DEH after realizing that he will always be a power-hungry tyrant and never reciprocate her feelings towards him.
The port city of Esparanza is an entire city of people who've crossed the event horizon. The city was set up by Valua right next to the Dark Rift with plans to cross through it into the skies beyond, but after repeated attempts to cross ended in failure Valua stopped funding any future voyages and withdrew from the city, leaving an old dreary rustbucket of a city full of people who've given up hope and are just waiting to die. Fortunately, Vyse's visit and eventual success in crossing the Dark Rift starts reigniting hope in the townspeople.
Gerald Robotnik crosses this hard in the Last Story of Sonic Adventure 2 when he finds out about Maria's death.
Shadow the Hedgehog can fall into this during certain endings of his titular video game (i.e. discovering that he is an android, believing that he is an experiment gone wrong). However, other endings he'll completely avert it. Ironically, no matter what happens, he will always end the story by saying, "This is who I am." Besides the Last Story, in which he says, "Goodbye forever, Shadow the Hedgehog."
Sonic hits this in Sonic Lost World. Despite continuing on, he's incredibly affected as everyone seemingly drops like flies thanks to his bull-headed stunt that led to the Deadly Six breaking free: his world has been sucked dry, Amy and Knuckles been hit with it, Tails captured by the villains, and for extra measure, he's forced to watch Eggman, Orbot and Cubot plunge into lava. He almost seems resigned when he sees Tails turned into a cyborg of sortsuntil he reveals that he's still in control and not a robot. Eggman even returns, ready to reclaim his victory and, at the end, everyone's revived. For such a bright and colorful game, it's probably also one of the darkest.
Walker's squad goes through one after they unknowingly use whitephosphorus on a refugee camp.
Walker himself goes through one at the end of the game when he realizes that he was hallucinating the villain, John Konrad; that he slaughtered a U.S. Army regiment; and that he has doomed the entire city of Dubai to die slowly of dehydration.
In Suikoden V, the Prince will hit this at the end of the game if you recruit less than 60 Stars of Destiny; he wanders off into the frozen mountains, utterly broken by his experiences.
Tales of Monkey Island Episode 5 has Guybrush virtually get to this point. He's dead, Elaine has willingly become LeChuck's demon bride, and has zapped him with voodoo root beer. "They're going to take over the world together... there's a demonic sword involved, it's over". Fortunately, Morgan gives him some Reverse Psychology to pick him back up again.
The second half of Leon's story in the remake of Tales of Destiny is all about breaking Leon down past this point until he ends up betraying his friends. Only his Heroic Sacrifice gives him any solace. In the original, his death is purely villainous, and he has to wait until the sequel for any sort of redemption. He does get better, though.
It isn't clearly shown onscreen, but the game's backstory makes it apparent that Mithos, Kratos, and Yuan all suffered this upon the death of Martel, Mithos's sister and Yuan's fiancee, leading the heroes of the ancient world to become villains instead. Kratos arguably claws his way back out of the Despair Event Horizon when he becomes disillusioned and meets his lover, Lloyd's mother, falls back in when he thinks they're both dead, and then claws back out again when he encounters Lloyd later.
Zelos spends much of the game near this line, despite hiding it, as his terrible childhood and lonely life gave him little self worth and no friends. Lloyd's friendship and trust helps him recover... until Flanoir, where Lloyd either confirms his trust or questions it. The latter sends Zelos over the Despair Event Horizon, and he later commits Suicide by Cop.
Tales of the World: Radiant Mythology has Kanonno, after her home world, Pasca, was consumed by war and mana abuse despite her efforts as its Descender. She even committed genocide, which led to Pasca's rapid decline.
In Hopeless Masquerade, the human villagers as a whole are on the brink of crossing the horizon, after the constant incidents causing problem after problem for them. Though it turns out that this is due to newborn youkai Hata no Kokoro siphoning hope from the villagers after losing her own Mask of Hope.
Twisted Metal Black has Preacher, an evangelist who, under Demonic Possession, slaughtered an entire church. He's competing for Calypso to remove the demon and clear his name. When he wins, Calypso tells him the truth: There's no demon. He's a schizophrenic who killed everyone in the church during a psychotic break. Preacher is so broken that he tries to get back in God's good graces by crucifying himself; when that doesn't work, he gives up and throws himself off of a building.
Chapter 11 of Uncharted 2: Among Thieves ends with Drake trying to carry a wounded Jeff, only for Chloe to turn against you. Once finally caught, Lazarevic takes your dagger and shoots Jeff dead. Only Drake and Elena are left to outrun an army of militia with the enemy gaining a complete upper advantage.
In We Happy Few, after A Very Bad Thing happened, the citizens of Wellington Wells were plagued by guilt and the desire to forget it to the point where they cannot go on without taking Joy, and react violently to any reminders of what the Bad Thing was or anyone that isn't taking Joy. You can witness Uncle Jack crossing it all over again when he gets a very direct reminder of what happened, and the niece that he lost, and the Joy isn't enough to wipe it away. He collapses into madness from both this and the realization that Wellington Wells is doomed because no one will stop their Joy usage no matter what happens, and ends his last broadcast assaulting everything he can see with a cricket bat screaming "WE'VE COME TO THE END OF OUR TIME!" again and again.
Wild ARMs 2: A certain Eldritch Abomination was sealed away "beyond the Event Horizon" in the backstory, and happens to be the source of the protagonist's Super Mode. Said protagonist is pushed to the edge of the Despair Event Horizon midway through, and teeters there for the entire game. After defeating the supposed final boss, which involves his Magnificent Bastard commander sacrificing himself to give an Eldritch Location a physical body to kill, he suffers a Heroic BSoD that almost releases the demon. In other words, his despair formed a bridge across the Event Horizon.
Xenoblade Chronicles 2 has this as one of its recurring themes, showing what despair does to those who wallow in it for too long:
Pyra/Mythra crossed it five hundred years prior, when Mythra was provoked into destroying a continent and its people. As a result, both have become death seekers by the time the story begins, wanting to go to Elysium in order to beg their father, the Architect, to destroy them.
Jin crossed it when Lora, his former driver, ended up dying while he became a Flesh Eater. Because of that, he ended up meeting Malos, and fed off of his desire to destroy the world, while Malos fed off of Jin's depression and sadness.
Amalthus crossed it after seeing a soldier whose life he had saved murder a family. As such, when he first awakened Malos and resonated with him, Malos inherited his misanthropy and hatred at the world, and used it as reason to wreak havoc on Alrest.
The Architect crossed it after inadvertently destroying his home world and becoming a god, while watching the new cycle of humanity he created commit the same mistakes as the last, and while also witnessing his other half's atrocities in another dimension. As a result, he did nothing to stop Amalthus and Malos's wrongs despite all his power, believing his attempted atonement to be doomed to failure.
Rex nearly crosses it when Pyra/Mythra allows herself to be captured by Torna, to the point where Rex nearly decides to return to life as a salvager, at least before the rest of the heroes give him a talking down for giving up so easily. As such, he ends up breaking the cycle once he speaks with Addam's spirit, and commits himself to fighting for other people's happiness and to prevent the cycle of despair and destruction from continuing.
Yakuza: At the end of the game, with his blood brother, love interest, and father figure all killed within hours of each other, Kiryu tells Date that he has nothing left to live for and resigns to going back to jail for the rest of his life. Date snaps him out of this by telling Kiryu that he still has someone worth fighting for: Haruka, the little girl whom Kiryu has been protecting for most of the game and who was recently revealed to be the daughter of Kiryu's late love. Kiryu recovers and goes on to make protecting Haruka his number one priority for the rest of the series.
Yandere Simulator: If anything happens that will prevent Ayano from being with her Senpai (such as being caught murdering, being expelled, or a rival successfully confessing her love to Senpai), an extra option on the game over menu called SNAP Mode allows Ayano to cross this, causing her to seek out a knife and kill Senpai, then herself, beating anyone who gets in her way to death with her bare hands.