From shit +‎ list, by analogy with hit list.

shitlist (plural shitlists)

1. (vulgar) A group of people held in contempt or targeted for revenge, etc.
   • 1961, Bernard Malamud, A New Life:

     “Gerald,” he said, trying to keep his voice steady, “if you countermand these recommendations I’ll have to go to everybody and tell them about Bullock’s shit-list that you did nothing about.”

   • 1981, Philip K. Dick, VALIS:

     unkies generally showed up to tell her which other junkies were doing the ripping off and the boasting. Sherri put their names down on her shit list.

   • 2017 March 24, “The G.O.P.’s Health-Care Failure: First Thoughts”, in The New Yorker:

     This afternoon, as Paul Ryan arrived at the White House to tell Donald Trump that he did not have the votes to pass the American Health Care Act, there were reports that the President’s chief strategist, Steve Bannon, had advised his boss to keep a “shit list” of all the Republicans who opposed the bill.

shitlist (third-person singular simple present shitlists, present participle shitlisting, simple past and past participle shitlisted)

1. (transitive, vulgar) To place on a shitlist.

   He refused to pay the protection money, so he's been shitlisted.

• hit lists, hitlists, stiltish