Iriana Estchell of Ilivais X lived a life that amounted to abusive rape followed by even more rape, which given her condition meant more like being tortured for 15 years. By the time the story starts, she's desperately trying to cover her mushy, fragile core with stoic badassery and indifferent sadism, but isn't as good at that as she'd like. When she meets someone that loves her (or rather, manipulated into doing so), she's so confused at how she's treated that she tends to respond by hurting her even more.
The Makeover Fairy is also pretty bad, trying so hard to be happy and girly and cheerful, but always showing in the end that she's just a Nervous Wreck.
Survival of the Fittest: Thanks to the premise, there are a fair amount of examples of this trope due to how many cuties are broken in each version. It's either that they started out this way and only get more scarred and/or Ax-Crazy, or that they become this way due to the amount of trauma they've suffered. Either way, the island doesn't do well for mental and emotional health.
Agent Carolina, in the present, is one of these, having built up a cold, callous exterior that covers her sadness concerning the fates of her Freelancer comrades. Like Wash below, hanging around the Reds and Blues have helped her immensely recover the kindness she used to have.
Agent Washington was once an Adorkable and friendly Nice Guy, until he had the memories of a tortured AI unit uploaded into his head. This, combined with the betrayals of various friends and allies later in life, led to Wash becoming cynical and no-nonsense. After the Blues help him escape custody, however, Wash begins to recover and becomes something closer to his kinder self.
In Season 12, it's implied and later confirmed that Felix's experiences in the Great War against the Covenant have kind of broken him and reshaped him into the cynical, sort of-Sociopathic Hero he is today. Nope, that's his cover story. He did fight in the war and it did have an effect on him, but he was a sociopath even then and arguably only got worse.
It's implied that Locus' experiences in the Great War have also left him with some form of trauma, which he hides with his One-Man Army and Consummate Professional mask. Unlike Felix, it's genuine, and Felix was willing to exploit this and keep him from getting help in order to keep him by his side so he could survive their work as mercenaries.
In Worm, Vista, the youngest member of the Brockton Bay Wards, becomes this after Leviathan's attack on the city kills two of her teammates-including one that she had a childhood crush on-and then seeing the rest of her team slowly collapse, eventually becoming The Fatalist and accepting what she viewed as her inevitable death while still doing everything she could for her teammates.
By the end of Volume 3, Yang has become this. First, she is publically disgraced and arrested on internationally broadcast television, then she's told her Missing Mom Raven is still around and also cares very little about her, and then she loses her school, her promising career, all of her friends (including Penny and Pyrrha, who are fatalities, and her team-mates in RWBY who all go their separate ways) and even her right arm in the devastating terrorist attack which destroys Beacon not long afterwards. The epilogue shows that even after several weeks have passed, the normally cheerful and easygoing Yang is bedridden and under her father's care, a depressed and emotionally broken girl who angrily admonishes Blake at the mention of her name and even brushes off Ruby's affection with little care. Poor thing.
Blake is introduced rejecting the idea of a happy world. Her past of leaving her family to remain a member of the White Fang, being in an abusive relationship with its leader, and finally going on the run to escape the violent ways of the organization left her emotionally damaged. It shows in her obsession with stopping Torchwick from collaborating with the White Fang, which compels her to throw away her health, grades, and sanity by not sleeping, eating, studying, or socializing. She also considers herself a coward, and hates herself for her past actions. The events that transpire during her confrontation with the White Fang's leader amidst the fall of Beacon (she gets beaten and stabbed, and watches her best friend lose her arm trying to defend her) enforce her beliefs that she doesn't deserve to be loved by anyone, and that she ought to shut herself away from the world. She also becomes paranoid, surly, ill-tempered, and physically abusive to Sun, whom she treats as a nuisance that doesn't comprehend the reality of what she is going through.
Max from Camp Camp is a cynical Jerkass, who feels the need to drag everybody else down to his level. But it is made painfully clear, that this is driven by the fact that his parents just don't give a shit about him and dumped him in rundown summer camp without even bothering to sign him up for a specific activity. Underneath that act is a heartbroken, lonely little kid.
Out of all of Amoridere's characters, Toki's the most overt case, as, she became bitter and cruel in response to her trauma of her Dark and Troubled Past, the which has losing her birth parents, being separated form her twin sister, being subject to an experiment, her being abused by her adoptive mother, almost succumbing to leukemia (her survival of which being miraculous), picking up on some new tricks, and developing mental illness. As we can see in some stories, Toki Used to Be a Sweet Kid.