Character name: Leanne Kerns
Superhero name: None yet of course but "Lepton" 

Appearance: Pale, with black wavy hair down to her shoulders. She has brown eyes, wears pretty vivid lipstick and paints her nails. She's around 5'6, with an athletically-built body and a thin, kind of bony face. She wears quite a bit of jewelry and enjoys scarves. 
Costume/physical changes: I'm not really sure about a costume, but probably just kind of blue-color range stuff over Kevlar. There's probably a picture of an atom on there somewhere but not really conspicuous. She is a simple woman in that regard. She wears gloves in case she does something really illegal and doesn't want to leave fingerprints, a mask just to be safe, and some colored contact lenses (blue!). 

Niche: Possibly speedster. She's quite good at breaking and entering if needed.

Power Source: Your average MMR shot....that wasn't your average MMR shot. She was too young to remember, but she started crying as a man in a white coat stormed into the small doctor's office and shouted at the top of his lungs "That's the wrong needle, you idiot!" Her mother was terrified, but was successfully (after a month or two) reassured that it was simply a vaccine for another nasty disease, that it would simply boost her immunity even more. Too afraid to complain that it burned and tingled and sent weird sensations up her arm, Leanne let the event slip slowly out of her memory. As far as she knows today, it was magic or ghosts or talking animals. 

Powers: Manipulation of electrons. For free-moving electrons, she can interrupt or start an electrical current, although this works best (obviously) if there's a complete circuit available, but she can electrify metals for short periods of time. For electrons bound to atoms, she can excite them and cause the object made up of those atoms to heat up. 
If she overuses her powers, she can screw up the bundle of nerves that makes the heart beat, or maybe throw her nerves out of balance and give herself a seizure. Really any electro/electrochemical component of her body is at risk. 

Defining moment: One seemingly normal day, a music player or something of that sort ran out of battery. She couldn't have been more irritated, but...out of the blue, it turned back on and started charging. She was feeling pretty faint for the rest of that day, but after testing out and refining her powers, she thought, "Well dang, that makes me sorta responsible to be a crime fighter of some kind"

Insight to personality:
Stream of consciousness is as follows: 
[i]Oh god, oh god, oh god. He has a gun. That's illegal isn't it? I don't know if it's illegal. He's going to shoot her, oh god, oh god--SHUT UP, SELF. DO SOMETHING, YOU HAVE SUPERPOWERS.[/i] 
Actions are as follows:
She doesn't move, and tries to be inconspicuous. She lifts her hand and squints hard at the gun. Concentrate, concentrate. Lives are at stake, damn it. The metal starts to glow orange after several painfully long seconds. Small threads of smoke begin to curl out from the man's jacket. Her mind makes time slow. Her heart is pounding. There are palpitations every other beat now, but it shouldn't take much longer. It won't be fatal to anyone, she reminds herself as a bit of remorse tugs at her; he'll just have a few burns. "Police," she orders the lady in a rare stern voice, "now." She turns away and covers her ears as the man tries to grab the superheated gun, evidently angered by Leanne's outburst. Luckily this is the main attraction, and she leaves the groceries and hurries out, the screaming and the smell of smoke ringing in her ears. 
-
She likes to think things over, and is especially uncomfortable in large crowds. Usually, she's quiet, patient and observant, and doesn't like to rush things. However, when she is with any handful of people she trusts, she spills stories and asks questions. She likes to call herself "Baddy McBadass" but this is a joking thing; apart from being humble, she's incredibly easy to defeat in hand-to-hand combat if she can't use her power. She doesn't like to hurt people, even "bad guys". She makes assumptions about people's personalities based on how they look and carry themselves, and tries her best to avoid those who look less friendly if she can.