Mephistophelean vs diabolic

Mephistophelean

adj
  • Showing the cunning or ingenuity or wickedness typical of a devil. 

diabolic

adj
  • Extremely evil or cruel. 

  • Showing wickedness typical of a devil. 

  • diabolic magic square 

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