Natural Enemy (1997) is a U.S./Canadian made-for-cable movie for HBO directed by Douglas Jackson. It stars Donald Sutherland, William McNamara, Lesley Ann Warren, and Lenore Zann.
Ted Robards (Donald Sutherland) is a businessman who has his hotshot young partner, Jeremy, (William McNamara) staying with him as a temporary house guest. What Ted doen't know is that Jeremy is the son of his second wife, who was adopted into an abusive family and is now a raving psychopath.
The spanking scenes
Lenore Zann plays Jeremy's slutty, masochistic girlfriend. In the first scene she is naked, face down on a couch with her wrists bound. There is a snake tattoo on her right ass cheek that he smacks with his hand. She begs for more and we see a close-up of his hand hitting her again, then her face as she receives a third smack.
Later, she is handcuffed to a dresser while they have rough doggie-style sex. Jeremy also beats her with a leather paddle. About to climax, she begs: "Do it harder!" and we see the paddle impact again.
With each paddle stroke, Jeremy has split-second flashbacks of the childhood belt-whippings his abusive step-father once gave him. We see only the father as he swings the belt; then, cigarette in hand, he leans toward the still unseen boy.
Jeremy recreates the scene, snuffing his cigarette out on his girlfriend's ass-cheek (again, on the snake tattoo). She screams in pain and complains, "That really hurt!"
"Don't I know it", he replies.