Opposite words for sensitive:
unaffected, soulless, painless, stout, insensitive, callous, unclassified, large, deadened, unreactive, insensible, rude, blunt, numb, thick, big, coarse, great, immense, indurate, dull, dead, heavy, pachydermatous, huge, clumsy, thick-skinned, tough-skinned.
Usage samples:
  1. Would other men be so sensitive to him?
    "One of Our Conquerors, Complete", George Meredith Last Updated: March 7, 2009.
  2. Her eyes stayed with him- large and sensitive, clear.
    "Joe Burke's Last Stand", John Moncure Wetterau.
  3. The chairman was not possessed of a very sensitive nature, or he would not have uttered this last sentiment.
    "The Man Who Rose Again", Joseph Hocking.
  4. A cloud fell over Daisy's sensitive face.
    "The-Motor-Girls-on-a-Tour", Penrose, Margaret.