cruel vs killer instinct

cruel

adj
  • Cool; awesome; neat. 

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

  • 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) 

killer instinct

noun
  • The natural inclination to do whatever is necessary to succeed (including extreme violence) 

  • Used other than figuratively or idiomatically: see killer, instinct. 

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