mercilessness vs tenderness

mercilessness

noun
  • The property of being merciless. 

tenderness

noun
  • pain or discomfort when an affected area is touched 

  • a tendency to express warm, compassionate feelings 

  • concern for the feelings or welfare of others 

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