SCP-042. A formerly winged horse, now in suicidal depression.
SCP-187 is a seer. Specifically, she sees whatever significant changes the things she's looking at will undergo. She had to be fed intravenously for months because whenever she looked at food, she saw it digested.
SCP-105, a normal teenage girl who was framed for the murder of her boyfriend and is now a prisoner for the rest of her life.
SCP-085 ("Cassy"), thanks to accidental exposure to the report on her nature, is now fully aware of her 2D status and her subsequent limitations. She immediately became clinically depressed at the realization as to how lonely she really was.
SCP-1324. An extraordinarily sensitive anteater that's harmed by even the faintest of stimuli, but just wants to be friendly to the personnel.
SCP-590. A young man who has the power to heal injuries, both mental and physical, with a touch, taking them into himself. The Foundation use him as a disease repository to clean out personnel who get sick. Then he was given mental retardation after being used to take so many injuries that they basically wiped out his mind as a form of Mercy Kill. This was done by Dr. Bright, who's SCP-590's brother. What makes it worse is the results of experimentation with SCP-978, the camera that shows you a photo of what a person desires when photographed.
Photographed Activity: Subject is playing with blocks.
Photo Result: SCP-590's face is close up to the camera, filling the entire photo. His hands are displayed as if pressed against the lens. His mouth is open, and tears fill his eyes.
SCP-054, a friendly undine who's psychologically scarred by several harsh experiments. She almost becomes a Woobie, Destroyer of Worlds.
SCP-507 is The Everyman who periodically shifts into crappy alternate earths every two weeks or so. When shifted back, he's reduced to a depressed wreck.
SCP-1951-a. A non malicious entity of living radiation. Unable to interact with regular people (as a few unlucky guards found out) he apparently made himself a family who were wiped out by Gv20 EMP grenades, due to the increased levels of radiation they were producing. The poor guy left a last message, and hasn't appeared again since.
SCP-1467, a man who's in a constant state of fading out of existence and will disappear completely if he isn't reminded of his own name periodically.
451, an agent who, after being exposed to some sort of anomalous artifact, became unable to see or communicate with anyone else, even indirectly. He thinks he's the only survivor of an apocalypse he caused and that the world is constantly altering for no apparent reason, and has repeatedly tried to commit suicide. The Foundation is trying to give him a fake Scrapbook Story to follow in order to keep his hopes up long enough for them to find a cure, but it's not clear how long that'll work...
The guy who created SCP-1976 as a Replacement Goldfish of himself for his family after he died of a brain tumor, only for it to not work at all the way he planned.
SCP-1504, who can't be killed and can't quite communicate or physically interact with anyone. Becomes rather less sympathetic when he kills half the Foundation staff at his site and, when that doesn't work, causes a mass containment breach that forces them to nuke themselves.
One of the D-Class used to communicate with SCP-1140 — an inter-dimensional being who's stuck in a drawer and needs people who are both easily suggestible and uncomprehending of whatever horrible things it wants them to do — was institutionalized as a child and later lobotomized. The author's comments reveal she and her twin sister were taking a bath when someone or something drowned her sister in front of her and she wouldn't or couldn't say what happened.
SCP-1926-2. Sure, Snoozee wasn't able to prevent the death of an epileptic child during its night terrors as a Mewt, but he's still a friendly toy who wants to get along with the other Mewts, even if they continue to abuse him.
SCP-239 during the events of Incident 239-B. She's being chased by a lunatic who wants to kill her, then was put in a medically induced coma and may be that way for the rest of her life.
SCP-321. Just read the entry on how hard her father tries to rescue her from a life of imprisonment and fails. According to Dr. Bright (Admin), who created her character she's Dr Bright's (Scientist) sister.
D-132 from SCP-1590's experiment log, with those rooms give you some hints about her traumatic life. Most importantly, the Room 32 indicates that she's innocent for the crime she was accused of.
SCP-818. Imagine SCP-239, but male, mute, severely autistic, and absolutely miserable. And then, just as he starts making progress in finally stopping his loop, they neutralize him.
SCP-1481, a drug-addicted Benevolent Genie who used to be all powerful that can't properly grant wishes anymore due to an owner wishing him to be an "alcoholic j-j-j-junkie tweaker crackhead" and making sure that the wish cannot be reversed.