[hatchet man] {n.}, {colloquial}
1. A politician or newspaper columnist whose job is to write and say unfavorable things about the opposition.
* /Bill Lerner is the hatchet man for the Mayor's Party; he smears all the other candidates regularly./
2. An executive officer in a firm whose job it is to fire superfluous personnel, cut back on the budget, etc., in short, to do the necessary but unpleasant things.
* /The firm hired Cranhart to be hatchet man; his title is that of Executive Vice President./