Melinda Sordino from Speak is very much depressed during her Freshman year in High School, and eventually, we find out that she has a very good reason to be so. Not only have her old friends drifted apart into different groups, leaving her to become a school outcast, but she also is a recovering rape victim.
In the Fingerprints series, Yana Savari does a good job of pretending to be a Genki Girl, but her backstory is revealed to be one big Break the Cutie. In the final book, her Broken Bird nature finally comes to the surface.
Hirsent from The Reynard Cycle is one of these. By the end of Defender of the Crown, she's endured the deaths of her husband and two of her children (one due to miscarriage, the other due to murder), and a rape. Hermeline refers to her as the "queen of ice."
Sansa Stark, Arya's older sister, doesn't fare much better. She has gone through a massive Break the HaughtyandBreak the Cutie process that involved all kinds of abuse and betrayals - only to end up as the protegée of Littlefinger, who is partly (entirely?) responsible for her father's death and most likely grooming her in the creepiest way.
In the Reboot Book Series, Wren 178 counts as this, since she died from being shot in the chest, then came back as a Reboot.
Winterhart from Mercedes Lackey's Mage Wars trilogy starts out as a classic example of this trope, right down to the tragic backstory, repressed emotion, and the Epiphany Therapy courtesy of the protagonist.
X-Wing Series character Dia Passik is a textbook example. Sold into slavery as a dancer, harbored a polite hatred for others of her species, generally ruthless, and sort of hostile to her teammates. Then she does a Shoot Your Mate (he seems dead, she tells us she thinks he was dead, but it's ambiguous) and has a Heroic B.S.O.D. in which she tries to commit suicide. The teammate who stops her ends up, eventually, in a relationship with her, and she defrosts.
Lessa in Dragonflight. She was 11 when her family was killed; she's first introduced at the end of ten years disguised as a drudge and living solely for revenge. Needless to say, she has a lot of issues. Impressing a dragon and an eventual romance do a lot to allay them, though, and in later books, she's a lot more stable and one of the most badass authority figures around. When F'lar asks her what she wants to do after her revenge is achieved, she has no idea because she was never able to think past that point.
Éowyn of Rohan has been forced to nursemaid an ailing uncle and endure the sexual harassment of his Evil Chancellor for years. Plus her cousin dying in the war, and her beloved older brother being imprisoned (or banished in The Film of the Book) for trying to protect her...Even the Witch-King's terror aura didn't seem worse to her than that. Thank God she gets better and befriends, and then marries, Faramir, the local Wise Prince.
Rían, daughter of Belegund. Lampshaded in Unfinished tales when it is told she was quite unlucky to be born in a hard time like the First Age. She married Huor after fleeing Dorthonion with the remnants of her family, and had only just conceived when the call came in. Then, she had to see her husband go away, and when she learned that he and everyone else from her people was killed and her country overrun, she gave her infant son to fostering among the elves, and went to die on her husband`s grave.
Morwen, Ríans cousin, fared even worse. When Húrin, her husband, finds her again after many years, she has been well and truly broken, and dies in his arms. Húrin spares her the suffering of knowing how their children met and what happened afterwards.
Vin from Mistborn, especially near the beginning. She was raised by her abusive Jerk Ass of an older half-brother to trust no one and be continually suspicious of people's motives- as the author puts it "she's not a bad person- she just thinks everyone else is." Learning how to trust and form meaningful bonds with others is the central thrust of her character development throughout the trilogy.
Noa Baek in Min Jin Lee’s 2017 novel “Pachinko” is in running for the king of this trope. Noa is born a zainichi, a minority group of Koreans immigrated to Japan, or born and raised in Japan, who suffer persecution. Noa had aspired to be a Self-Made Man and went to university in the 1960s. When he discovers that he had only managed university because his mother was friends with a Yakuza, it breaks him and he abandons his family and takes on the identity of Nobuo Ban, a meek pachinko game operator.
Things get worse from there: his mother uses her Yakuza friend to track him down and begs for reconciliation. He agrees, but after she leaves he commits suicide. He genuinely loved his family, but it destroyed him to know that he would never escape his identity as a minority member in Japan.
Leitha from The Redemption of Althalus is emotionally detached, very snarky, and traumatized by having to hear the thoughts of everyone she meets. Nearly getting burned at the stake didn't help. And on top of that, very, very good at hiding just how much she's hurting. Luckily, like most examples, she gets better.
Thalia Grace. Her mother was an abusive alcoholic who neglected her and her brother, Jason. Eventually, she ran away, only to find herself constantly being attacked by monsters and having to fight to survive. She sacrificed her life to save her friends, and spent seven years as a pine tree. As a result of all this, she's sarcastic and cold. She gets better after the third book.
Annabeth, due to the trauma from losing Thalia, and later Luke.
In the sequel series, Reyna becomes one in Mark of Athena. She already had a Dark and Troubled Past, losing her home and being captured by pirates. In the third book, it gets worse; a war breaks out between the Greeks and Romans, destroying her hope of anything good happening ever again.
Nico is a male example of this trope. His mother died, he was stuck in the Lotus Hotel and Casino for sixty years, his big sister Bianca died, his crush Percy fell in love with Annabeth, he believes nobody likes him because he's a son of Hades and therefore pushes everyone away... by the last book he's absolutely shocked and can't understand it when Reyna, Coach Hedge, and Will are still willing to sta friends with him.
The heroine of The Sirantha Jax Series (Sirantha Jax) was involved in a tragic accident that left her lover and scores of people dead. It broke her rather badly, and she's in the beginning stages of recovery at the start of the story.
Sinai from Black Dogs. She blames the tragic fate of her cousin on herself and becomes a Death Seeker bent on revenge.
Lily Bard in Charlaine Harris's Shakespeare series, due to her having been gangraped, tortured (leaving her body permanently scarred), then left for dead.
When we meet Rochalla in the first of the Shadowleague books, she fits this trope perfectly, though she (oddly enough) gets better when she is forced to flee for her life with a bunch of strangers.
All K-named reincarnations (It Makes Sense in Context) in Kim Stanley Robinson's The Years of Rice and Salt. This starts with the very first, Kyu, who is abducted from his home as a child, castrated and horribly disfigured on a boat in the middle of nowhere, and finally mobbed to death by an enraged populace (one of the other characters remarks, after he comes out of his fever after said castration, that he's a different person altogether), and continues on with all sorts of unpleasantness. In fact, much of the overarching conflict is based on this particular soul's Broken Bird status.
Talia (Sleeping Beauty) from The Princess Series is an almost textbook example of this since her tragic past causes her to have a very stoic, sarcastic, and violent attitude.
Mira's group of university friends in Marilyn French's The Women's Room are varying degrees of this trope, except possibly Iso. Chris becomes one after her rape, and Mira herself is one by the end of the book.
Susan Jagger of Dean Koontz's False Memory. She's crippled by agoraphobia so severe she can't even look out her apartment windows, and is completely convinced somebody is somehow breaking into her apartment at night and raping her. She's right, too. Her agoraphobia was planted by her psychiatrist, who puts her into a hypnotic trance so he can get into her apartment and not just rape her, but Mind Rape her into playing whatever sick games he devises. These are all calculated to make her cry, because he gets off on her tears. He breaks her for his own amusement...and she's not the first person he's done that to, either.
Nicci's abusive and bafflingly-misguided mother and Brother Narev turned a nice, sweet little girl into a Sister of the Dark and servant of the Imperial Order. Her backstory lingers a lot on how much she's actually this under her armor of unfeelingness, in lurid, horrifying, and tragic detail. An unusual example because she spends most of a year trying to fix herself, but being so broken, goes about it in a completely ridiculous way. Despite that, she manages to get healed, but not at all how she expects.
Richard himself after being tortured by Denna for a month. So that "no mental damage" thing he appeared to escape captivity with? Heh. He had actually become insane, but kept it under wraps except for certain triggers that would immediately break him down. It took a lot of Fridge Logic and growing up for him to snap out of it. He does end up healing himself, too (This is historically before the Nicci example, but hers is much more prominent).
This is actually how you make a Mord-Sith. It's actually more horrible than it sounds. Richard humanizing his Mord-Sith detachments is one of the most heartwarming moments of the series.
Both Arpazia and her daughter Coira in White as Snow. After her rape, Arpazia goes into lengthy trances where she forgets reality and her face is often described as an eggshell when she is being particularly stoic. Coira's only strong emotion was love for her mother until Arpazia wounded her. After that, she refused to feel much of anything.
Lucy in Someone Else's War, a young woman who has been with the LRA since she was six and has had at least one child born of rape.
Johanna Mason was a victor of a previous Hunger Games, and because she refused to go into prostitution, she lost everyone she loved. She appears cold and nasty, but is simply hardened from losing everyone.
Katniss Everdeen herself has shades of this after her father's death, but gets much worse as the series goes on, especially after her trip to the arena. She becomes a more literal example during the events of Mockingjay with her role as the Mockingjay for the rebellion.
Her mother, Mrs. Everdeen. After her husband's death, she went into a near-catatonic depression. She eventually got better, but then her oldest daughter becomes a tribute in the Games, twice, her District gets blown to ashes, and her youngest daughter dies. Not at all hard to see why she never returned to District 12.
Dieda from Forest House is repeatedly confused with her niece, Eilan, whom she resembles almost identically. She is chosen by a priestess by the High Priestess when mistaken for her niece, despite being in love and soon to be engaged to Cynric. When Eilan is pregnant despite having made a vow of chastity, Dieda is required to take her place to alleviate confusion. Cynric is killed after slapping Eilan when Eilan is High Priestess, and most of her family is killed and Dieda kills herself
Attolia of the Queen's Thief series is renowned by foreigners and her own subjects, who are all dog-loyal, for being cold, ruthless, and unlovable. It’s heavily implied throughout the second book that this is due to her shattered childhood when her parents were killed—she was abruptly placed on the throne, humiliatingly forced to submit to a war between her power-hungry barons, driven into an arranged marriage with a man she hated, and earned the terror of her entire country by poisoning him at their wedding feast. She’s spent the years since unable to trust anyone, and the one person she does actually trust to some degree (Relius) ends up betraying her. By the end of the third book, however, with her marriage to Gen, she’s started to undergo defrosting.
Lori herself is somewhat subtly depicted this way. Mostly this comes out in her retellings of the "Aunt Dimity" stories in the introductory book. Under the terms of the will, Willis Sr. has her recount several of the stories, first to identify herself as the rightful heir, then as proof that she's researching the correspondence Dimity Westwood and her mother Beth left behind. She begins to notice that the versions she recalls have some telling differences from the tales as originally told in the letters—differences which reflect her own bitterness over her divorce and poverty, the robbery of her humble apartment, and the loss of her mother while she was living in another city.
This is Bree Pym's backstory as it unfolds in Aunt Dimity Down Under. Her grandfather recently died, her abusive alcoholic father went on one last bender, and she fled the situation, only to find her long-lost mother had remarried and started another family (in part to forget her own sufferings at the hands of Ed Pym). She finds and quits a couple of jobs, gets several tattoos and numerous piercings, and is so upset when the tattoo artist advises her to slow down she trashes his studio and breaks his glasses. Of herself, she tells Lori:
"Ex-cons have trouble adjusting to life after prison. I disappointed my teachers by not going to university. I haven't been able to hold on to a job since I left Takapuna. I attacked Roger for no good reason, and I expect I'll do the same to Holly. I don't know how to behave around normal people." She pressed her hands to her eyes. "I've given up hope of learning."
Star Wars Expanded Universe: Mara Jade. Taken from her family by the Emperor, who probably had them killed, and indoctrinated and turned her into his personal assassin. The one mission she fails, killing Luke Skywalker, comes back to bite her hard when Luke subsequently triggers Vader's Heel–Face Turn and killing of the Emperor to protect his son. Oh, and the Emperor was in telepathic contact with Mara at the time and showed her a false vision of what happened (Vader and Luke turning on the Emperor together) to say "This is all your fault," with the vision tormenting her practically nightly for five years to ensure that eventually she kills Luke as vengeance on Vader from beyond the grave. She loses her power and prestige, her home and sense of purpose, and spends five years bouncing from meaningless job to meaningless job, often having to take off when her latent Force abilities awaken and the visions of the Emperor return, and she fears to let anyone get close. Then she meets Luke Skywalker and discovers that her existence has been a lie, and everything she ever believed was wrong. Timothy Zahn picked her name for a reason.
Song at Dawn: Poor Alis. She's lured into Raymond de Toulouse's clutches with a marriage proposal he never intended to keep, chained in his bedroom, raped, and then put on display before his vassals. After that she's a nervous wreck with failing health and her jealousy of Estela goes Up to Eleven because she believes herself to be Defiled Forever.
The Chalet School, of all places, has a resident example in the form of Grizel Cochrane, the bitter, sarcastic music teacher. Her mother dies, her father marries a woman who treats Grizel like dirt, her grandmother - the one relative she had who really loved her - dies, and she ends up being forced into doing a job she hates by her parents, when she'd rather be teaching PT. She takes her unhappiness out on her pupils, many of whom are terrified of her, and Joey can't reform her. To cap it all, when she moves to Australia to start a new life with an old school friend (who nearly killed her with a stone in their school days), said friend runs off with her fiance. She does get a happy ending, but not until late into the series.
Angel in Redeeming Love is deeply embittered and cynical as a result of being raped as a child and then forced into prostitution until she was in her early twenties. The novel’s main premise is one man’s divinely-appointed attempt to reverse these effects via The Power of Love.
Elisandra in Summers at Castle Auburn has to maintain her perfect calm at all times, because going along with the machinations around her is the only way to keep it together.
Dolores Price of She's Come Undone. Abusive father, raped at thirteen, lost her mother to a truck accident, bullied for her weight, attempted suicide, institutionalized for seven years, and married an abusive idiot who forced her to have an abortion.
In "De skandalösa" by Simona Ahrnstedt, Magdalena Swärd becomes this after she was betrayed by her fiancé. She becomes very cynical and reluctant to trust a man.
A large part of Children of the Night deals with the protagonist, Diana Tregarde, trying to recover emotionally after note before the novel starts nearly being killed by a mystic being.
The Red Vixen Adventures: Salli at the start of Captive of the Red Vixen, having shut herself away after divorcing her abusive husband. She gets better later in the series with therapy, but she still suffers from depression and panic attacks when off her meds.
In different ways, both Glynn and Ember from The Legendsong Saga. Ember is dieing from a brain tumour and has completely devoted the rest of her life to accepting this fact; Glynn is struggling with having been The Unfavorite, and the fact that everyone she cares about (her sister, her parents, her mentor/friend/dream-boyfriend)are all dead/dying. Glynn, at least, gets better through her love for Solen and link with the He-feinna.
Snow White in Six-Gun Snow White is pretty emotionally broken after years of physical, verbal, emotional, and borderline sexual abuse from her stepmother.
Every Surgebinder in The Stormlight Archive. It's an important part of the process; their soul needs to be broken in order to be reforged as something stronger, through a bond with their spren. Kaladin was an apprentice surgeon and master spearman who lost everything due to the careless actions of a few nobles, while Shallan's Abusive Parents crushed her spirit and nearly destroyed her entire family before she killed them—her mother when she was a child, and her father about a decade later. Lift, from the interludes, doesn't have as much focus, but she's an orphan who apparently saw horrible things in her homeland. Dalinar grew up as a bloodthirsty soldier, always second best, to the point that he almost killed his brother for his wife and throne. While he suppressed that urge, he still bears the weight of the guilt from that moment, not to mention that he was dead drunk when his brother was assassinated. And of course there is Renarin, an Ill Boy who grew up in as a non-combatant in a Proud Warrior Race, and who always had to live in the shadows of his father and brother.
Brenda from The Maze Runner Trilogy. Parents dead, living in a city filled with degenerating cannibals, and has a disease that will turn herself into one. The possibility of a cure from the Gladers is what gets her going.
Lake Monroe in the Broken Love Series due to having been bullied for a decade. Keiran Masters is in an even worse shape from having been groomed as an assassin since he was a toddler. Also Keenan Masters, Diana Fulton and Sheldon Chambers.
Gaia Moore in Fearless Series due to losing her family, starting with witnessing her mother's death-by-shooting at the hands of her jaded uncle and her father's subsequently abandoning her. As the series progresses, Gaia also witnesses the death of Mary Moss, her first true friend; is manipulated into believing that her first love, Sam, was murdered because of her; sees her former enemy-turned-ally, Ella Niven, sacrifice herself to save her; is abducted, experimented on, and almost killed multiple times; learns that Sam wasn't actually killed but rather taken into captivity for over a year; is manipulated into believing that her father is dead; and sees her boyfriend, Jake, killed in a last-ditch effort to save her. In spite of being clinically unable to feel fear, Gaia is quite a tragic figure.
In Room, MaNote name revealed to be Joy in the movie was kidnapped at 17 years old and locked in a small 10x10 room everyday for the next seven years. During this time, her kidnapper raped her almost nightly, resulting in her getting pregnant twice, one leading to a painful miscarriage and the second resulting in Jack, the protagonist. When she finally gets out, she's noted by relatives to be far more bitter than she used to be, and despite loving her son immensely, her PTSD leads her to unthinkingly snap at him at times when he brings up the room casually and without understanding the full extent of what she went through due to his youth.
Anne Bronte's The Tenant of Wildfell Hall has the heroine, Helen Graham, who was once a Wide-Eyed Idealist girl who married a Byronic Hero husband, believing she could change his unsavory habits and lifestyle for the better. She turned out to be dead wrong and suffered from years of abuse before she finally fled to live in the abandoned Wildfell Hall in order to protect her son from her husband's influence. It's honestly no wonder why she's so distant and cold towards most people, including Love Interest Gilbert Markham.
She was taken in by her grandmother who also didn't care much about her. Maya took care of herself while her grandmother smoked and drank; occasionally having to hide from her grandmother's lawn boy who was also a pedophile. Then her grandmother dropped dead and Maya disappeared rather than risk being sent back to her parents or some other uncaring relation.
She was doing well enough on her own in the Big Applesauce, living under the name Inara in a loft apartment with a dozen other waitresses from the same restaurant. Then she's kidnapped by the Gardener who takes her to his Garden; tattoos a butterfly on her back, assigns her a new name, and rapes her. She lives among the other Butterflies in their Glassy Prison waiting until he kills her on her twenty-first birthday.
The Hearts We Sold: Dee's life has sucked, to put it mildly. She grew up in an abusive home, and while she's managed to escape by going to boarding school, the plot begins when she finds out her scholarship is going to be revoked. And that's before she makes a Deal with the Devil.
Nezumi from Broken Gate can be inferred to be this, as, prior to the events of the story, she was mistreated by her older brother, Ryuuji, which culminated into a fight, in which she placed a curse on him, offering an escape clause. Unfortunately, he took that chance to antagonize her more, causing her to open the gate in a fit of retaliation. With her guarding her gate and knowing she's going to die, along with the events the came before, it's not surprising that she's become emotionless (right down to even feeling them), as her circumstances probably robbed her of the ability to cope otherwise.