Yeah I think Audrina had the worst circumstances. Not only the gang rape on her birthday(which was terrible), but what happened afterward. She ended up forgetting and went through life thinking she was crazy.
I think Carrie was another one who had it bad. She only had happiness for about five years of her life and then had to be locked away. It was unfortunate for Chris and Cathy too, but at least they were older and weren't at such a vulnerable age as the twins were. Carrie lost Cory who was her only best friend and then went through life thinking she was bad because the Grandmother put that in her head when she was five. She ends up thinking she can't marry the one man who loves her because of that.