play the heavy, to

To do that which is necessary but undesirable or unpleasant, especially behaving in a mean, strict, or unsympathetic manner. My wife is all cuddles and kisses with the kids, then I have to play the heavy when they misbehave. I know you don't like playing the heavy, but your employees will never respect you don't lay down the law.

Fig. to act the part of a mean person; to do the unpleasant tasks that no one else wants to do. (Refers originally to playing the role of someone evil in a movie, etc.) I'm a nice guy, but at work, I am required to play the heavy. The boss makes me do all the cruel things.

Act the part of a villain; take the blame for unkind behavior. For example, She can't bear firing an employee, so she relies on Jim to play the heavy. This colloquial term comes from the theater, where heavy has been used for a stern, serious role or that of a villain since the early 1800s.

To take the role of villain; by extension, to take the blame for meanness, cruelty, and other undesirable behavior. The adjective heavy was used to describe the villain’s part in theater from about 1800 on, and by 1900 heavy was being used as a noun for such a role. Only in the mid-twentieth century was it extended to offstage events, as in J. D. Salinger’s Franny and Zooey (1962): “I’m sick to death of being the heavy in everyone’s life.”