Nice family meets another seemingly nice family, realizes that family is not so nice, but is too nice/weak to actually get away from them, and then ends up being killed by the not so nice family.

Just once I would love for the nice family to see the writing on the wall and strike first, even if there is a question of "maybe we over reacted and they weren't going to kill us," only to find undeniable proof that did the right thing and their murdering of the bad family was 100% justified. I'd pay to see that.