harsh vs merciless

harsh

adj
  • Severe or cruel. 

  • Unpleasantly rough to the touch or other senses. 

verb
  • To negatively criticize. 

  • To put a damper on (a mood). 

merciless

adj
  • Showing no mercy; cruel and pitiless. 

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