The Collaborative International Dictionary of English v.0.48:

Vindictive \Vin*dic"tive\, a. [For vindicative, confused with L.
   vindicta revenge, punishment, fr. vindicare to vindicate. Cf.
   Vindicative.]
   1. Disposed to revenge; prompted or characterized by revenge;
      revengeful.
      [1913 Webster]

            I am vindictive enough to repel force by force.
                                                  --Dryden.
      [1913 Webster]

   2. Punitive. [Obs.]
      [1913 Webster]

   Vindictive damages. (Law) See under Damage, n.
      [1913 Webster] -- Vin*dic"tive*ly, adv. --
      Vin*dic"tive*ness, n.
      [1913 Webster]

WordNet (r) 3.0 (2006):

vindictively
    adv 1: in a vindictive, revengeful manner; "he plotted
           vindictively against his former superiors" [syn:
           revengefully, vengefully, vindictively]