Source : Webster's Revised Unabridged Dictionary (1913)

Annihilative \An*ni"hi*la*tive\, a.
   Serving to annihilate; destructive.

Source : WordNet®

annihilative
     adj : wreaking or capable of wreaking complete destruction;
           "possessing annihilative power"; "a devastating
           hurricane"; "the guns opened a withering fire" [syn: {annihilating},
            {devastating}, {withering}]