The Collaborative International Dictionary of English v.0.48:

Unamiable \Un*a"mi*a*ble\, a.
   Not amiable; morose; ill-natured; repulsive. --
   Un*a"mi*a*bly, adv.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

31 Moby Thesaurus words for "unamiable":
   chill, chilly, cold, cool, disaccordant, disagreeable, frosty, icy,
   ill, incompatible, inhospitable, inimical, strained, tense,
   unaffectionate, unamicable, unbenign, unbenignant, uncompassionate,
   uncompassioned, uncordial, unfriendly, ungenial, ungracious,
   unharmonious, unkind, unkindly, unloving, unsociable,
   unsympathetic, unsympathizing