Antonyms of contentious:
unargumentative, uncontroversial, noncontroversial, anti-imperialist, antimilitarist, unwarlike, affable, amiable, amicable, benevolent, complaisant, conciliatory, cordial, easygoing, friendly, genial, good-natured, good-tempered, gracious, ingratiating, kindhearted, obliging, pleasant, sociable, calm, quiet, relaxed, serene, tranquil, benign, gentle, kindly, mild, nonaggressive, nonbelligerent, pacific, peaceable, peaceful, unbelligerent, uncombative, uncontentious, acquiescent, agreeable, amenable, compliant, complying, cooperative, docile, obedient, submissive, tractable, incontestable, incontrovertible, indisputable, indubitable, undeniable, unquestionable, irrefutable, uncontested, undisputed, safe.
Examples of usage:
  1. The contentious men having been removed, it will be profitable that the rest agree on one form of words.
    "Historical Introductions to the Symbolical Books of the Evangelical Lutheran Church", Friedrich Bente.
  2. " Such noble- minded champions must be very cautious, though," said Rhodopis, " lest they become contentious, and quarrelsome.
    "The Complete Historical Romances of Georg Ebers", Georg Ebers.
  3. A man who over a great part of the north was in labour concerns the unquestioned master of many legions, and whose political position had hitherto been one of conspicuous moderation, even to his own hurt, had given Wharton the warmest possible backing; had endorsed his proposals, to their most contentious and doubtful details, and in a few generous though still perhaps ambiguous words had let the House see what he personally thought of the services rendered to labour as a whole during the past five years, and to the weak and scattered group of Labour members in particular, since his entrance into Parliament, by the young and brilliant man beside him.
    "Marcella", Mrs. Humphry Ward.