Opposite words for incentive:
counterincentive, deterrence, disincentive.
Usage samples:
  1. This necessity was an additional incentive to action, and Balzac's letters to Madame Hanska about this time, contain several indications of his anxiety about " Les Paysans."
    "Honore de Balzac, His Life and Writings", Mary F. Sandars.
  2. Maybe I should never have had the courage without that incentive.
    "The Guests Of Hercules", C. N. Williamson and A. M. Williamson.
  3. My recommendations will concentrate this job- creation tax incentive in areas where the unemployment rate now runs over 7 percent.
    "Complete State of the Union Addresses from 1790 to the Present", Various.
  4. It is a good token for the future that men shall feel their labour is appreciated, although a desire for official recognition may be no incentive to the devotion itself.
    "Memoir of William Watts McNair", J. E. Howard.