Everyone in this movie is awful
Perhaps that's the point.
It's hard to have sympathy for one single person here. Nick's a dumbass who cheats on his wife even after she's missing, Amy is a batshit woman scorned, Desi a manipulative control freak, Rhonda a blinders-on cop who is just after Nick, Tanner a slick willy lawyer, Ellen the Nancy Grace of the movie...
it really made the ending so important. Perhaps, in the end, they deserved each other.