mercilessness vs wickedness

mercilessness

noun
  • The property of being merciless. 

wickedness

noun
  • The state of being wicked; evil disposition; immorality. 

  • A wicked or sinful thing or act; morally bad or objectionable behaviour. 

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