fiendishness

from The Collaborative International Dictionary of English v.0.48

Fiendish \Fiend"ish\, a.
   Like a fiend; diabolically wicked or cruel; infernal;
   malignant; devilish; hellish. -- {Fiend"ish*ly}, adv. --
   {Fiend"ish*ness}, n.
   [1913 Webster]