The most common themes/motives displayed in these 3 particular films are mental disorders, obsessions, seeking approval from family, revenge, violence, sex, loneliness, fear, power, death, status, coincidence, childhoods, desperation, torture and twists. Although these are found to be linked to many other films, the way they are presented and used as crucial components of the plot is what could potentially weaken the foundations of the film.
For example, the theme of a murderous family in "The Devil's Rejects" could have taken all uniqueness away from the film and caused the audience to assume it was "just another", but the use of the theme of a strong family and presentation of them being united in their cause saved it, and it is rare to see a conventional American family that openly admit to being murderous animals. The contrast adds a dark humour and an interest in their behaviours, as they switch from killers to a family, and sometimes become both at once. We as an audience begin to ask questions about how they came to be this way, and become more and more aware of the flickers of the themes as the film goes on.
