bad apple vs diabolical

bad apple

noun
  • A person who is not wholesome, honest, or trustworthy, especially one who has an adverse influence on others. 

diabolical

adj
  • Extremely wicked or cruel. 

  • Of or concerning the devil; satanic. 

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