Another word for WEAK

Toni can only be described as one thing: Definitely NOT ordinary. She lives alone. Has the fighting abilities of a professional assassin and is a target for the bullies at her school *cough* prison *cough*. But she isn't THAT alone. Marcus, an old man almost on his deathbed, helps her become the fighter she is. But what is he training her for?

But in a twisted turn of events, Marcus got mugged and murdered. But no one would even dare lay a finger on the old man so Toni was sure it was an assassination. She set out to kill whoever murdered Marcus but her brain gets twisted. She doesn't know what to think. Is she fighting for good? Bad? Herself? Or is she a pawn in someone else's plan?