The Collaborative International Dictionary of English v.0.48:

Antagonistic \An*tag`o*nis"tic\, Antagonistical
\An*tag`o*nis"tic*al\, a.
   Opposing in combat, combating; contending or acting against;
   as, antagonistic forces. -- An*tag`o*nis"tic*al*ly, adv.
   [1913 Webster]

         They were distinct, adverse, even antagonistic.
                                                  --Milman.
   [1913 Webster]