WordNet sense 1 (impossible to reconcile):

irreconcilable, unreconcilable

WordNet sense 2 (not friendly):

inimical, unfriendly

WordNet sense 3 (proceeding from or exhibiting great hostility or animosity):

bitter

WordNet sense 4 (characterized by antagonism or antipathy):

antagonistic

WordNet sense 5 (characteristic of an enemy or one eager to fight):

aggressive, belligerent

WordNet sense 6 (very unfavorable to life or growth):

uncongenial

WordNet sense 7 (not encouraging or approving or pleasing):

unfavorable, unfavourable