The Collaborative International Dictionary of English v.0.48:

Diabolize \Di*ab"o*lize\, v. t.
   To render diabolical. [R.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

diabolize
    v 1: turn into a devil or make devilish; "Man devilized by war"
         [syn: devilize, devilise, diabolize, diabolise]