If you've still got the room, I've got a fun little idea.
Essentially, a relatively normal person, but with a large apparent potential for meta-human power. For them, it wasnt so much the power offered, but the money for their family (who needed the cash). They were pressured into it by their family. Unfortunately, it had a rather nasty(but mostly benign) side effect. It created a split personality. Minor changes in powers between the two. One is a front line brick / blaster, the other is more of a stealthy brawler. One is outgoing, the life of the party, and while they'll help people, they wont do so just because, there will always be a reason, even if its because they think the person asking for help looks cute/handsome. The other(the host) is more the sort who cares about everyone, and truly wants to help(but is very much of a wallflower in ways).
Updating for more details.
She was selected for the program, and things went well, until she actually had to use her powers, at which point, something strange happened. She snapped, and an alternate personality developed. The two of them are in many ways different, in fact, they even have subtly different powers.
Sin is good at front line combat, and can hit them at a distance with some kind of a molecular destabilizing energy. She can also use this in direct melee combat, making her a most dangerous opponent to face.
Adriana lacks the control of molecular destabilizing energy that Sin has, but can cloak herself, vanishing from sight, and can remain that way, apparently indefinitely. Outside of her cloaking ability, she appears to have a lessened version of Sin's energy, and can inflict a moderate amount of damage with punches, kicks and the like, but they dont have the raw damaging capacity that Sin's attacks have.
The two of them have a sort of agreement, and somehow, they've managed to cope and handle the stress of training and sharing one body. For now anyway.
In short, Sin can use Corrosion, and hit targets at range. Adriana is limited to being able to vanish(concealment), and can dish out damage(via strike) in direct melee.
Sin is more about raw power, while Adriana is more about proper skill and usage of the power that she has at her disposal.
