cruel vs relentless

cruel

adj
  • Intentionally causing or reveling in pain and suffering; merciless, heartless. 

  • Cool; awesome; neat. 

  • Harsh; severe. 

adv
  • To a great degree; terribly. 

verb
  • To violently provoke (a child) in the belief that this will make them more assertive. 

  • To spoil or ruin (one's chance of success) 

relentless

adj
  • Unrelenting or unyielding in severity. 

  • Unremitting, steady and persistent. 

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