Antonyms of contentment:
discontent, discontentedness, discontentment, misery, sadness, unhappiness, wretchedness, anguish, desolation, joylessness, sorrow, woe, dejection, depression, despondency, dispiritedness, gloom, melancholy, aggravation, annoyance, exasperation, irritation, pique, vexation, anger, fury, rage, agitation, distress, disturbance, upset, discomfort, restlessness, uneasiness, displeasure, dissatisfaction.
Examples of usage:
  1. I preferred my coffee, and the contentment which my mind experienced at our success.
    "How I Found Livingstone", Sir Henry M. Stanley.
  2. The pure enjoyed the gifts of paradise in peace and contentment.
    "The Complete Historical Romances of Georg Ebers", Georg Ebers.
  3. Henceforward he had no choice but to sink to a baser contentment, or else rise to a higher self- devotion.
    "The Gospel According to St. Mark", G. A. Chadwick.