Antonyms of incentive:
deterrence, disincentive, counterincentive.
Examples of usage:
  1. There remained, with this one exception, a nucleus of earnest, thoughtful people whose creed was in part the creed of the Internationale, the creed of universal brotherhood, equality before the law, purity of individual living as an example and an incentive to a national purity.
    "The Maids of Paradise", Robert W. (Robert William) Chambers.
  2. To play for people is not only a good incentive for further aspirations; it also furnishes you with a fairly exact estimate of your abilities and shortcomings, and indicates thereby the road to improvement.
    "Piano Playing With Piano Questions Answered", Josef Hofmann.
  3. There is nothing for him to do, and if there were, there is no incentive for him to do it.
    "Humanly Speaking", Samuel McChord Crothers.