Okay: here's a rough start. Do the powers/weaknesses look alright?
Xi Xiu / 20 / Female
Appearance:
Short, slim, but clearly very fit. Xiu is unnaturally pale, a large, round face, and buggy eyes. Her head is mostly shaved, with dark ponytails hanging off either side. She has large scars across various parts of her body, including between some of her ribs, at her joints, along her spine, and down her thighs, but most of them are thankfully hidden by her uniform. In spite of this, her face somehow has a natural "cuteness" to it.
Powers/Abilities:
Super Reflexes and Agility - Xiu can run faster, jump higher, swim deeper, and think and act quicker than normal humans. Her abilities aren't nearly as noticeable as most of her classmates, which contributed to the government taking such a long time to classify her as a malfunction in the first place. She can't shoot anything out of her hands, control things with her mind, or even lift a car, but she has no problem overwhelming any opponent in physical combat, simply by outpacing them and wearing them down. She doesn't get tired from physical strain, in the same way normal people do. She can force herself to keep going, and doesn't seem to suffer any long-term side-effects from this strain.
Hyper-Reactive Eyes - The utility of Xiu's eyes extend far beyond that of normal humans. They are far more sensitive to movement, able to see from far greater distances, and can adjust far further and faster than normal humans. Her pupils can expand and contract unnaturally far, granting her natural night-vision, and protecting her from being blinded by bright lights.
Weaknesses/Limitations:
Neurotic - Xiu is constantly stiff and in a state of stress and discomfort about her surroundings. She does her best to hide it, but it regularly manifests in pulling her own hair out and chewing on non-edible things. Without drugs or very specific (comfortable, tranquil, loving, etc) circumstances, she's neither open, nor sociable in any way. The concept of "relax" doesn't register as an option.
Non-Functioning Eyelids - Xiu is unable to fully close her large, buggy eyes. The best she can manage is a minor squint. As such, she constantly has to keep a small dropper handy, to rehydrate her eyes.
Numb - Xiu has several severed nerve endings, meaning she often can't feel if something's in contact with her, or if she has a bleeding wound. She can still feel, especially in areas away from her scars, but her sense of touch is still far less reliable than most people.
Personality:
Xiu is a broken person. Deep down, she's very loving, very passionate, and believes in the good of humanity, but this mindset is buried deep, beneath a mountain of trauma and survival instinct. Survival is a serious concern for her, so she's always on her toes, unable to relax around others. She goes so far as to intentionally make herself look unattractive, even scary, as it motivates those around her to take her seriously, and not bother her without good reason. She falls asleep every night dreaming of nice house, with a husband and a dog, and wakes up every morning in a cold sweat, ready to fight to the death.
Backstory:
Xiu was born in district 13. She underwent several tests before her powers were discovered. As one of older students to test positive, she was selected to undergo a series of intrusive operations, exploring potential ways to harness and build upon her abilities. These experiments were unfathomably painful and disturbing for Xiu, who was left with severe Post-Traumatic Stress Disorder. Nonetheless, the result was deemed a success, as her actual physical capabilities were outstanding, and, more importantly, controllable. When she had fully recovered from her operations, nearly a year later, she was shipped off, ready to begin training.
More docile than most Malfunctions, they decided to test further new methods of Malfunction-handling on her. Rather than more conventional forms of transportation, Xiu was shipped to the facility in a small steel box, barely alive by the time they pulled her out.
When her training began, her muscles quickly grew back to their former strength, and she again became a point of interest. There was something fascinating to the facility staff, about how simple her powers were, and yet how effective they wound up being. She couldn't display anything outstanding, that would catch one's eye from a distance, but she simply excelled at every single task she was given. She was just fast enough to be too fast, just perceptive enough to be too perceptive, just strong enough to be too strong, just resourceful enough to be too resourceful, and she never seemed to get tired. It was unsettling... and hypnotizing.
Talents/Skills:
Xiu is very good at problem solving, and games like chess. She's also proficient with knives, polearms, and hand-to-hand combat.
Quirks/Habits/Other:
TL/DR:
A compact, maladjusted fitness freak.