mean streak

plural mean streaks

1. idiomaticA defect in character characterized by persistent nastiness, viciousness, or malevolence.

   England’s combative coach . . . wants aggression, a touch of the outlaw, a mean streak.

   2016 March 10, Paul Hayward, “Sport: Eddie Jones takes England siege mentality to the extreme”, in Telegraph, UK, retrieved 14 Sep 2017

   2 more examples

   "He's worse than mischievous," Mr. Lane assured her sourly. "There's a mean streak in that family."

   1911, Charlotte Perkins Gilman, chapter 1, in The Crux

   The film's considerable taste for graphic, noisy violence becomes clear during this tumultuous opening. So does its mean streak, as the Colonel delivers outrageous insults to one and all.

   1993 May 14, Janet Maslin, “Film: A Western in the Hands of a Revisionist”, in New York Times, retrieved 14 Sep 2017