The Collaborative International Dictionary of English v.0.48:

Out-Herod \Out-Her"od\, v. t.
   To surpass (Herod) in violence or wickedness; to exceed in
   any vicious or offensive particular. Compare outpope the
   Pope. "It out-Herods Herod." --Shak.
   [1913 Webster]

         Out-Heroding the preposterous fashions of the times.
                                                  --Sir W.
                                                  Scott.
   [1913 Webster]

WordNet (r) 3.0 (2006):

out-herod
    v 1: surpass someone in cruelty or evil