Karine...
... or rather Karen, should have been the heroine. I don't know if it was the filmmakers intent on taking out the likely hero and heroine first for shock value - and I am not inclined to give him credit for that considering what a pooper this devolved into - but I think a HUGE mistake was made not having her character carry the film.
Hands down, both women were stronger characters than their male companions but I didn't feel as much for Chloe. Her flashbacks were trite and felt very out of place and underdeveloped and she lost all credibility at the end when she didn't finish him off.
When Karen died, I kinda tuned out. She was smart and supportive by helping Luke(OMGKILLHIMNOW), nearly dies on the bridge but soldiers on, single-handedly saves Luke and William, takes charge in the search for her boyfriend and then saves Chloe - Who sooo should have died in that pit trap. Srsly. When she finally does crack, it is very believable but still brief as she sucks it up and gets back to work... Not to mention, she was super cute in that girl-next-door way. :)