Toki's past and if they are to be believed started is this, particularly so when she tried to runaway from them and, as Brownie put it She was once sweet and only wanted to be loved. Lets see? Here they are:
She was abused and then neglected causing her to almost die of leukemia, during the events of Flashbacks I, something that caused something in her to drive her insane in the next incident (see below)
She returned to the place where she was once abused so she can get hold of the inheritance money but went insane during the events of Insanity and Resentment and has had issues eve since.
Frailine (the one Toki abused) is also an example as per these statements:
She was imprisoned for being criminally insane after the events of Little Girl's Revenge when she almost killed Toki and damaged the border between this world and the next. Kind of a Disproportionate Retribution, compared to what Toki did to her (abused her and then, sometime afterward, she sent to Alaska attached to a bus by a magnet with no means of getting home)
Sometime after being imprisoned, she almost kills herself twice and is never seen again, as per stated, in Diary of a Borderline Schizophrenic, driving Toki into more self-hate because of it.
Bunny and Madgie's parents died in an accident when Bunny was twenty and Madgie was nine.
Doki was separated from her twin sister Toki at when both were going on thirteen and was sedated and frozen.
Before leaving his home planet on the Dionysian, Fiearius Soliveré of "Caelum Lex" worked as an assassin for the dubious government organization the Society, potentially murdering many innocents. This culminated in an event that caused both his wife and four year old son to be killed.
The twins Vex'ahlia and Vax'ildan were taken from their loving human mother by their elven father, whose Fantastic Racism towards half-elves led to years of abuse and dismissal. The twins eventually ran away to try to return to their mother, only to find out that while they were gone, she was killed in a dragon attack.
Grog's refusal to kill Pike's grandfather led to him being disowned by his father Stonejaw, and ousted from his tribe by his uncle Kevdak.
Percy's entire family save for his sister Cassandra was murdered when the Briarwoods staged a coup in Whitestone, and Percy himself was brutally tortured for information that he didn't even have.
From campaign 2:
Caleb was made a student of Trent Ikithon along with his classmates Astrid and Eodwulf, to be trained as a Vollstrecker. This training was brutal and abusive, and involved him regularly torturing and killing supposed traitors to the Empire, and being experimented on by Ikithon by having residuum crystals implanted in his skin. Finally, Ikithon planted false memories into all three of his students' minds, leading to them murdering their own parents. This event shattered Caleb mentally, and he spent the next 11 years in an asylum.
Nott used to be Veth Brenatto, a halfling woman from the town of Felderwin. She, her husband Yeza, and their infant son Luc were abducted by goblins, and held prisoner for weeks. They eventually escaped, but in her attempt to create a distraction to allow Yeza and Luc to get away, Veth accidentally killed the leader of the tribe. His wife enlisted the help of a hag to make Veth suffer, and she was subsequently drowned in a river, reincarnated as a goblin, and kept as a slave for several years before managing to escape.
Beauregard grew up with an abusive father and a complacent mother, and became an angry teenage delinquent to spite them. After she got caught stealing again, her father paid to have her abducted and trained by the Cobalt Soul, and slapped her in the face as she was taken away. Several months into her training at the Soul, Beau received a letter from her parents stating that they'd since had the son they'd always wanted, and didn't want to see her again.
Fjord grew up in an orphanage that exploited children for their labor, and was viciously bullied for being a half-orc. To try to combat this, he spent years filing down his tusks to appear more "normal".
Jester is the daughter of the Ruby of the Sea, and knowing the Ruby had a child would be very bad for her reputation. This, combined with her mother's agoraphobia, led to Jester spending the majority of her childhood indoors, lonely and friendless, before she was approached by the Traveler.
Yasha was disowned from her tribe for marrying someone she wasn't betrothed to, and her illegitimate wife Zuala was murdered in her absence. She wandered aimlessly for ages until she was found by Obann, who brainwashed her into becoming his own personal killing machine. She was eventually saved by the Stormlord, but it wasn't until she met Mollymauk that she began to feel like anyone cared for her again.
Mollymauk woke up two years before the start of the story, buried in a shallow grave without any memories. The circus found him near-catatonic, naked and filthy and only able to say the word "empty". Molly has zero desire to figure out who he used to be before losing his memory and considers that person "dead and not me", but during a drug trip he confesses to Beau that sometimes he hates that he never really had a childhood.
Caduceus was the only one to stay behind in the Blooming Grove while his parents and siblings all left to find a solution to the Savalirwood's corruption, but as months turned into years, none of his family members returned. He later confesses that the isolation became too much for him to bear, and he started regularly eating lily petals to try to induce visions from the Wildmother, despite the fact that lilies are toxic and would make him horribly ill.
From campaign 3:
Laudna was one of the people hung from the Sun Tree as examples in campaign 1. When she came back from the dead as a Hollow One, she was chased out of her home and spent years wandering the earth, living in remote huts in the woods before nearby towns would inevitably get suspicious of her and chase her away.
Ashton was severely injured during a robbery gone wrong, and the Meatgrinder Surgery that saved their life left them with severe chronic pain. Afterwards, they learned that their group, the Nobodies, had abandoned them when it looked like he wasn't going to survive, and while he doesn't fault them for it, it's clear he's still angry and upset at the loss. On top of that, the person he tried to rob figured out his identity, and blackmailed him into working for her by threatening to turn him in if he didn't.
Josephine was viciously bullied both at school and online, betrayed by someone she thought was a friend, and raised by an abusive, alcoholic aunt. This has all contributed to her present self's unhealthy sense of paranoia. Fortunately, she's since been Happily Adopted, and has slowly been working on getting better.
Zia's father shot himself when she was eight, she was bullied at school for her outsider status and acne-ridden skin, and then her mother got diagnosed with cancer and required Zia's constant care, leading to most of Zia's friends moving ahead in life and leaving her behind. She's since gained many more friends, and her mother has recovered, but she's still been left with a morbid depression that she hides behind an upbeat facade.
Jessica's mother was severely traumatised after her boyfriend and parents were killed in a bungled robbery. She sought out old flames for a series of one-night stands, which is how Jessica was born. She's spent most of her time since caring for her reclusive mother, which in turn has left her ostracized and fed into her jerkass personality.
While most of Edward's upbringing was normal, he's had to endure a slew of intense physical surgeries to help with his cerebral palsy. This has had a traumatic effect on him, to the point that he briefly considered suicide. He since doesn't try to think about it.
Daigo was the result of a one-night stand between his celebrity father and his lower-class Japanese mother, the latter of which has now passed away. He was then subject to physical, homophobic, and racist abuse by his father and step-mother, until he eventually fought back and poisoned the latter to death. His tumultuous upbringing has caused him to regard himself as a villain, and contributed to his desire to become a leader through any means necessary.
Trixie Maialini on Dina Marino: It's known she has drug use issues and she comments that she never had many good things from life. It's implied there's even more trauma to be discovered.
The Opening Narration of Doom House explains how the wife of the main character, Reginald P. Linux, had died long ago and that this had left a severe depression weighed heavy on his soul.
Par for the course in Fallout Is Dragons. Granted, it's set in a post-apocalyptic wasteland, but thus far two player characters are former raiders, one was abandoned by his mentor after nearly damning a filly, one was physically and psychologically tortured by his own "teacher", one was forced to kill his own brother for no other reason then to amuse the Big Bad, and one lost his memory, leg, and EYES in an explosion. And that's not even factoring in the NPC backstories...
Jeanette of Funny Business is revealed to have this in the flashback. It turns out that having omnipotent power from a young age can do a number on one's psyche.
When you put them all together, even though they're played for dark laughs, a lot of bad things have happened (that weren't actually his fault) to The Nostalgia Critic. Abusive Parents, hiding in the cupboard when he got scared, breaking up with someone three times and getting stalked for it, pitied by his classmates for acting like a brat, date-raped on his prom night, and that's just what we know so far. No wonder he's a weepy Psychopathic Manchild with issues.
The Nostalgia Chick had a judging mother and an emotionally distant father who both were alcoholics and yelled at each other constantly, had an uncle that molested her, got bullied at school for being the awkward dork, became an alcoholic herself and somehow got fixated on guys she could fix and control to do whatever she asked of them.
The crew of captain Icomb's ship in Skies Unbroken has: two former Sky Pirates (including the good captain himself), one not-so-former Sky Pirate who joins later, a soldier whose side lost The War Just Before, and a Waif Prophet. It's their passenger's Dark and Troubled Past that is, however, most frequently (if vaguely) alluded to.
Madiha Nakar from The Solstice War is an amnesiac orphan and is hinted at having done a lot of horrible things as a child during her country's revolutionary war, where she fought on the socialist side.
Touhou: a Glimmer of an Outside World has many, many indications that Yuuka wasn't quite as mentally stable as she is in the roleplay in the past. Like a basement with a room full of torture equipment.
Atli in Njal Gets Burned very obviously has one, but neither Njal nor Bergthora care enough to ask for any details.
and only wanted to be loved. Lets see? Here they are: