ameliorate vs twist the knife

ameliorate

verb
  • To make better, or improve, something perceived to be in a negative condition. 

  • To become better; improve. 

twist the knife

verb
  • To deliberately do or say something to worsen a difficult situation or increase a person's distress, irritation, or anger. 

How often have the words ameliorate and twist the knife occurred in a corpus of books? (source: Google Ngram Viewer )