Destroy Me, Please is a fanfic where the protagonist plans to kill themselves. They demolish their house in order to leave nothing behind. Isabelle catches them mid-suicide attempt and saves them in the end.
In Chapter Forty-Four of A Triangleinthe Stars, all of Bill's depressing thoughts, and eventually suicidal thoughts, ultimately lead up to him taking this route, via lightning bolt, hoping it would overload him and finish what his parents had started. He fully and truly believed the world would be better off without him, that every single person hates him and wants him dead (which is and was actually true but for three genuine exceptions), and that he shouldn't have existed in the first place. He also had done such reprehensible things that he was almost constantly mentally being given hell over. Thankfully, after protecting him from the bolt Steven manages to talk him down, with a Cool Down Hug to boot.
In The Prayer Warriors, which features Harry Potter, Percy Jackson, and the Carter Kane Chronicles, there are a few cases.
Percy Jackson, after converting, considers killing himself. It's later indicated that Grover felt the same way as well.
After Grover dies as a result of a failed attempt to exorcise the demon within him, Annabeth commits suicide.
In the originalBad Future of Zero 2 A Revision universe, Demon managed to kill off the entire Digidestined before dying to Omnimon. Having lost all their spirit due to their partner's death, the remaining Digimon (X-Veemon, Angewomon, and Omnimon) decides to kill themselves and each other. They ended up being Killed Off for Real after this, while they will be reborn in the Primary Village, they will not be the same Digimon that had appeared before death.
In the alternate ending for the first Ed Abuse (which the author has removed for being too dark), after Ed not forgiving Sarah for her actions just before dying, she can not bear with the guilt and kills herself.
After failing to save Emmeryn in Pretender, Robin attempts to hang himself thinking that he failed the only reason Chrom took him as a tactician in the first place. Frederick saves him before he can succeed and talks him down from committing any future attempts.
Strawberry Gashes is a fic about Elsa having suicidal and self harm tendencies most of her life.
Darkness Burning takes place in an Alternate Universe where Elsa's and Anna's parents didn't die. After Anna is sent away to live with her new husband, Elsa's depression and self-loathing continues to escalate until she attempts suicide. She survives but is deemed "ill". The rest of the fic is about her recovery and her relationship with her family.
In My Immortal, Draco commits suicide at one point, leading Ebony to attempt the same. Draco is alive the next time he's mentioned.
In The Queen Who Fell To Earth, Harry is more affected by the negative opinions surrounding the Triwizard Tournament than in canon. He walks out to the first challenge with his wand in his pocket and thanks everyone present for providing a way to rejoin his parents.
In Flying Harry jumps off the Astronomy Tower after Umbridge tells him that due to a new Ministry regulation he's required to marry a sadistic man several decades his senior.
Some Semblance of Meaning: Depressed about the bleak future that awaits him in the arena, Kit tries to kill himself by jumping off the roof of the Training Center, only to be stopped by the force fields. He ponders whether or not it would be easier to just end his own life than to go through the horrors of the Games on other occasions, as well. Also, Blake, the blind boy from District Eleven, actually did commit suicide after he and his district partner escaped the bloodbath.
This is the eventual fate of the main character Loivissa from the "A Dance of Shadow and Light" series by Ocadioan. And just to top it off, her fate was only revealed in a sidestory to the main series, at the end of an otherwise cheerful(for the series anyway) poem that she wrote herself shortly before her suicide.
Queen of All Oni: A flashback in one interlude chapter reveals that Blankman's father shot himself after losing the family fortune and using what was left to secure his son's future.
The Ultimate Evil: It's eventually revealed that Lo Pei's daughter Mei impaled herself with a sword after being taken as a bride and forced to watch her beloved one's murder by Shendu shortly before his imprisonment in his statue form.
In Second Story Window, we have this with Ryuuko, who is five, and, the narrator, Satsuki (her age isn't mentioned) who jumps out the titular second story window as an attempt to escape their psychotic mother Ragyo, the which they do survive. Also in the story, it was mentioned that, in the same year, Rei had hanged herself in the room where Satsuki and Ryuuko were hiding and she did so out of fear. In chapter 2, when it is told from Ragyo's perspective, Satsuki had attempted suicide by jumping through the titular second story window, after dropping her sister out of it. True to the aforementioned POV, Rei still hanged herself, although Ragyo doesn't know her reasons.
Played straight to a heartbreaking effect in Fragile Thread when Mako after she summons Ryuuko (who works as a prostitute), to her side to be with her in her last moments and while disclosing her motives. She dies as the story ends. It was mentioned that Ryuuko's mother had killed herself, leaving her to be the first to find her body.
In Maim de Maim, Nui, as an attempt to keep her split personality from taking and so she could die as herself. However, due to her genetic makeup, she fails.
Rei in Frozen due to the guilt she felt over past events.
Once again, this is reprised in chapter III of Cellar Secrets, when she commits suicide for similar reasons or, rather, because of what she knew, leaving her motives and the titular cellar secret to be revealed in her diary.
A mentally ill and traumatized Ryuuko in Ch. 17 of Concerning a Drifter attempts suicide in the ruins of her old home by overdosing on pills but Satsuki manages to intervene and get her to a hospital.
"Sora folded his hands behind his head and stared at the wall. On it was a small calendar that said '_ days without attempting suicide.' With an inappropriate smiley next to it. The blank was filled in with 14, but looked worn down from being erased over and over... He had never gone beyond one month..."
In The Legend of Link: Lucky Number 13, the twelve scientists responsible for Varia and Takara's torment are punished severely for their crimes (by being Forced to Watch the brutal murder of their families), leading eleven of them to immediately cut their own throats with a dagger.
Considering what the Mane Six have spent the last thousand years doing while under Discord's corruption in the Pony POV SeriesDark World timeline, it's understandable Rainbow Dash feels this way when she discovers Discord's Sadistic Choices were all lies and she failed to kill Twilight and get Discord to reset time to before his reign. She doesn't even struggle when Rarity tries to rip out her Element and even tells the others to let her. They even have to leave her on what amounts to suicide watch for a time. She later admits after recovering that if they hadn't, she might actually have torn her Element out to end it and thanks them for stopping her.
Dark World!Fluttershy later admits that by the time Cadance saved her soul from her psychotic daughter, she had gotten to the point where she wanted to die to end both her suffering and the suffering Cruelty had caused others.
In The Best Night Ever, Prince Blueblood goes through a phase where he kills himself in ever more elaborate ways due to Sanity Slippage caused by being trapped in a "Groundhog Day" Loop that forces him to relive the day of the disastrous Grand Galloping Gala over and over and over again. Killing himself only makes the loop start over quicker.
In Pages Of Harmony, Rainbow Dash kills herself through Autocannibalism after believing that any sense of loyalty has to be purged from her due to the Mind Rape that Twilight performs on her.. And she still behaves that way after she dies.
In The Light Never Goes Out, Rarity attempts this when she sees a letter from Sweetie Belle when she dies. Unfortunately for her, her attempts to slit her hooves with scissors fails due to her immortality.
Too Far deals with Dinky doing this after Diamond Tiara's bullying goes too far, jumping off a cliff. In the end, Discord gives Diamond, who has seen the consequences of her actions on the town, a chance to Set Right What Once Went Wrong and this is avoided.
Misunderstandings During his attempt to escape from Canterlot, Peter encounters Princess Celestia. The reason she approached was to get him to surrender himself, wanting to help. Unable to communicate with her, aware of her vast power, and thinking she is there to kill him- or worse- for being a threat to her ponies, he puts on gun to his head. Thankfully it didn't go off. Celestia herself is dismayed she could appear threatening to an individual unacquainted with her.
Sveti's father himself committed suicide. Big Top blackmailed him with knowledge of his Interspecies Romance. When Sveti learned of it, she offered to work as Big Top's exhibit. Her disappearance and Big Top's continued extortion drove him to suicide.
Sunset Shimmer, unable to deal with with feeling all the pain she'd caused due to being hit by the power of the Elements and the hatred of the entire school (which got so bad that she occasionally had to go to the nurse), tried to walk off a bridge, and was only stopped by Human!Twilight.
This happened with Granny Pie, but the exact circumstances of this are still unclear. It's later revealed that Hearing Voices affects whichever Pie family member has Pinkie's abilities each generation, and many end up taking their own lives.
An interesting twist on this trope shows up at the end of Just Us Little Ponies. After finally realizing that no matter what he does, Princess Luna will never restore his political power, Duke Greengrass attempts a form of political suicide. He makes a bargain with Archduke Fisher to restore his power in exchange for taking down Baron Mounty Max, but does so while he knows Max is evesdropping. Greengrass knows that when Max reports him he will be stripped of his titles and the last vestiges of his power, but this will also take out the corrupt Fisher and give Baron Max's career a boost (and Max is one of the few members of the Night Court Greengrass actually respects).
In Cheerilee's Garden Twilight throws herself off a roof when she realizes even Celestia thinks she murdered all of Cheerilee's victims. Too late, Celestia realizes that Twilight was innocent and concludes that a society that drove her student to her death didn't deserve to live, resolving to raze Equestria and form a new Solar Empire.
In A Teacher's Glory Temari suffes this after being captured during the invasion. Sick and unable to use chakra, she attempts suicide-by-ANBU by stealing a knife and attempting to force them to kill her. Also, after the Third Hokage's death, his closest advisors officially, but only one actually choose to join him out of respect.
Before the beginning of the story Asuka had tried to commit suicide several times. Daniel remarked that she would attempt to kill herself again sooner or later unless she got help.
Shinji also thought about killing himself several times as he was exiled in Boston.
Advice and Trust: In chapter 8, Ritsuko was so depressed because she'd committed all kind of crimes for the love of a man who didn't care about her that she started drinking wine copiously after taking painkillers. And then she attempted to take more pills, knowing fully well what would happen if she mixed sedatives and alcohol.
‘You’re halfway into your fourth bottle of wine and trying to take more pills. You’re a goddam doctor, Ritsuko. Are we still going to pretend you don’t remember what happens when you mix sedatives and alcohol at this dosage? Are we still pretending this isn’t a half-assed suicide attempt?’
The Child of Love: Shortly after her birthday Asuka could not take it anymore and locked herself in the bathroom and swallowed a bottle of sleeping pills.
Doing It Right This Time: In the immediate aftermath of Third Impact, with the whole of humanity wiped out and the world in ruins, Shinji and Asuka ended up walking into the sea together; they didn't know if they'd enter Instrumentality or drown, and neither of them really cared by that point. Instead, they ended up going back in time. Then Shinji nearly ends up putting a bullet through his head when they meet up just after the Third Angel happens, and he realises she remembers everything, including the whole "Dude, She's Like, in a Coma!" incident he thought she was unconscious for. This is not his last fit of self-destructive behaviour, but fortunately Misato and his fellow pilots are aware of it and doing their best to help.
Evangelion 303: After her failure with the NF-14 Asuka was so angry with herself that she decided to shoot herself. However she was ultimately unable to go through with it.
A line in chapter 12 suggests that she has attempted to commit suicide before the beginning of the story.
HERZ: Seven years before the start of the story Shinji slit his wrists after an argument with Asuka because he believed that she hated him and never wanted to see him again. The scene was very similar to Asuka’s own suicide attempt during the series.
Asuka had once felt like dying too, several times in fact, but there was always something that kept her going. No, not always. She had wandered the streets for days. She had starved herself. She had stripped naked and climbed into that bathtub. And she had waited, her life meaningless, her pride destroyed, her whole being slowly slipping from reality.
Once More with Feeling: Invoked. After Shinji reveals his whole story to him, Kaji wonders how the kid has kept himself from "eating the gun", so to speak.
The One I Love Is: Asuka had been completely beaten, humiliated and even MindRaped, after which she knew she would be replaced. She regarded herself as an utter, worthless failure, and the only thing keeping her from falling apart completely was Shinji loving her. However, when she thought Shinji had chosen Rei over her, she lost her only reason to live left. She wrote a good-bye note, ran away and slit her wrists. Fortunately she got found in time to save her life.
When Gendo arrives in Terminal Dogma and finds that Rei isn't there he tries to kill himself in a last ditch attempt to be with Yui again. It doesn't work.
The epilogue reveals that two SEELE members also tried to do it to escape arrest after their group was publicly exposed by Kaji. One succeeded, the other didn't.
RE-TAKE, the most famous Evangelion doujinshi series, does this to Rei, who hangs herself after being rejected by Shinji. The fact that before when she was confessing to him she splashed red paint on her self to make it red and chanted "anta baka" makes even more chilling.
In Pokémon Mystery Dungeon: Defenders of Warmth, Vulpix committed suicide as a human as part of a deal with Kuyurem to ensure she becomes important. Kuyurem simply wants to devour her spirit. She is turned into a vulpix and, ironically, becomes important as the Hero who awakens Reshirem, and thus becomes instrumental in defeating Kuyurem.
In Olivine Romance, Jasmine decides to take her own life as a result of a string of relentless abuses and hardships, including a loss of her home, job, and Pokemon, the betrayal of her friends, and the hateful treatment by her own mother.
In the side-story Path of Least Resistance, Volkner is confronted by Morty after a suicide attempt. The trigger was Volkner's guilt over failing to intervene in his childhood friend's suicide.
My Time Of Dying starts with Scourge's attempted suicide, and the whole story is about his struggle with depression, with him trying to take his life or deliberately indulging in suicidal behaviour multiple times.
Plankton in Plankton's Eye View, after seeing everyone become a success in the ten years he was imprisoned after The Movie. He became so bitter about his failures and how it was too late for him to redeem himself and make things right. However, The Flying Dutchman gave him a second chance.'
In Tiptoeing The Edge En Pointe Pearl attempts suicide after Steven's birth. She is stopped but continues to exhibit suicidal ideations for around a year after Rose's death. Her starting to develop feelings for Steven helps make her become less suicidal.
Duty Calls is a drabble where Pearl has suicidal thoughts during Steven's infancy.
Touhou Ibunshu has this as the impetus behind the fifth and eleventh arcs, Remixed Cherry Blossom and Reenactable Night, with Yukari and Mokou implementing schemes to end Gensokyo in the hopes it will end their endless existences. The former chooses life after a fully-deserved Villainous Breakdown after being confronted by Ran and Chen, while the latter gets her wish. Earlier, Reisen and Youmu are so consumed by guilt by losing the last Lunarian child to Remilia and being duped into aiding Yukari's scheme, respectively, that they try to commit suicide. Both are saved in time and calm down, Reisen by Tewi and Youmu by Yuyuko.
In Chapter 44: Early Preludes to a New Winter of Sorrow of Gensokyo 20XXI, Eirin, surprisingly, succeeds in killing herself (by severing an artery), dying with a smile to know that she could. She is supposed to be immortal but her willingness to die overrode her ability to resurrect upon death, effectively granting her wish, even though her motivation was unclear at the most. It is never exactly stated why she killed herself, besides, "Is it wrong to want to feel death, even though if one cannot experience it?" but it is implied that she killed herself out of the uncertainty of their situation, which caused her a lot of stress (leading to her developing anemia and to suffer from alopecia) and depression and, apparently, she might have done so way of escaping capture.
In 20XXIII, we do eventually find out her reasons for suicide and it was because of all the hell and uncertainty. The entire diary entry was basically her suicide note
Later on, in 20XXIV, we have Ran, chapter 9, after a near-miss with a rogue male kitsune. According to Mokou, she's attempted suicide more than twice by slitting her wrists. She fails at it nonetheless. She attempts it again when she think she's killed Reimu. In Chapter 62, she was apparently contemplating it. Later on, we have Chen, in chapter 60, attempting suicide drowning herself, that of which she gave no motives for and probably can't on the grounds that brain damage from said failed suicide attempt possibly rendered her unable to talk, however, it is known that she wanted her mom back and had given up on life, which would be as far as motives go. Two chapters later, she does seem to have her motives somewhat explained in her suicide note, the which Flandre finds.
In 20XXI, we have Nitori attempting suicide by ramming herself into wall, the which could have broken her neck. She failed.
In 20XXIV and The Unsaid Rivalry of the Youkai and the Shrine Maiden, we had Yukari contemplating suicide due to whatever sadness and pain she was suffering. Both times she is convinced not to.
Of all places, this fanfic: prior to being Dave's father, he had a wife and child, Amandine and Ava; watching one of them die was one thing but losing another in the war made him jump off the waterfall. However, he lives and gets better.