Opposite words for unfairness:
fair-mindedness, integrity, impartiality, lawfulness, fair play, honesty, candor, uprightness, equitableness, candour, righteousness, justice, honor, cricket, right, faithfulness, fairness, rectitude, equity.
Usage samples:
  1. There is a manifest unfairness in letting all the burden be borne by the willing horse.
    "Aphorisms and Reflections from the works of T. H. Huxley", Thomas Henry Huxley.
  2. And I would have reminded them of the extended popularity of their performance, and that it was an unfairness to muzzle the ox that treadeth upon one's corn, appealing to them to stand up for their rights, and refuse to compete except for the honorarium of a quid pro quo.
    "Baboo Jabberjee, B.A.", F. Anstey.
  3. The old war between private ownership, with all its greed and unfairness to the common citizen, and government control, with all its cumbersome and often inefficient methods, had reached acute proportions in the great northern province.
    "The Enchanted Canyon", Honoré Willsie Morrow.
  4. Thus he would refer to the shape of Madonna Lampiada's sumptuous eyelids, and to her shell- like ears, to the correct length and shape of Madonna Amororrisca's nose, to the lily tower of Madonna Verdespina's throat; nor would the unabashed old Florentine shrink from calling attention to the unfairness of Madonna Selvaggia's covering up her dainty bosom, just as he was about to discourse upon " those two hills of snow and of roses with two little crowns of fine rubies on their peaks."
    "The Quest of the Golden Girl", Richard le Gallienne.