I suppose in their own way they all have issues and flaws. But Peyton to me ever since the pilot has been the 'broken' one, we all see her pain & she is known for being dark & being down.
Brooke came a close second to me, as she has always felt as though she is not enough, not smart enough, not pretty enough, her parents never wanted her and she grew up alone. She has had her heart broken many a time & love always seems to pass her by -this has left her unstable emotionally & she now has major trust issues, and has trouble letting everybody in.
Haley, to me is the most stable out of all of them & has always had a good head on her shoulders & all in all has had an Ok ride, the only thing i would say that has touched Haley would be her sister being a screw up, this lead to her feeling as though she had to be extra amazing to make it up to her mom & dad & make them proud.
Lucas, his head is usually all over the place, he is indecisive & can never fully make up his mind. Not being wanted buy his father always effected him -he is the 'brooding' one.
Nathan, is the third most screwed up to me, motly because of famil y -he had a manipulative, controlling father, Dan & he had deb for a mother, a drunken mess -he had it rough and was always pushed into being the golden boy, his family has let him down all his life -leaving him with issues.
Then you have Peyton, this girl from season ne you could see was emotionally broken in every way, she would never let anybody in & everytime anybody even went to get close BANG -down came the shutters, she lost her mother, found out she was adopted, struggled with drugs -went through numerous breakdowns -sho can blame her! She all in all gets he award for having the toughest life, she will always be the 'dark, mysterious' one.

^ You pretty much covered everything lol
They all are in a way but Peyton has been through so much, it just seems she has been the the most emotionally

Or Brooke

Agree with Amyonetreehill.

Peyton has had the most to deal with. Because of the things that have happened to her she was always slightly on the darkside :D however, emotionally she's very strong and thus has managed to overcome everything that's happened to her and gone on to have a happy relationship, family and life.

Brooke's felt unwanted since she was a child and while she is a strong person, emotionally she's not strong - I'd say because of her childhood. Things hit her harder than they do Haley or Peyton, for her, emotional hits are deeper and they take longer to heal. Most likely because she's so insecure and doesn't think as much of her self as she should, which is really sad.

At some point all of them have been.

AMYonetreehill said it all.

I would say it's either B or P.

I feel that Brooke has had the worst not to say Peyton hasn't gone through a lot she just puts it out there and lets everyone know she's broken. Brooke hides it but she's still so so so broken.

and Peyton

brooke and peyton.

Brooke by far then Peyton...then Haley and then the rest (: