Opposite words for gentle:
ill-natured, breezy, morose, lowborn, ill-conditioned, knavish, noisy, crabbed, raucous, resounding, ungenteel, piercing, lower-class, rough, blustering, bitter, blustery, plain, shrill, abrading, clamorous, squealing, clear, grating, brazen, squally, strident, thunderous, ringing, abrasive, ordinary, grim, deafening, foul, lowly, stern, booming, caustic, forceful, stentorian, stormy, forcible, untamed, stiff, abased, rainy, thundering, disagreeable, acrimonious, obstreperous, earsplitting, misty, inferior, powerful, ill-tempered, strong, irritating, discordant, intense, foggy, scathing, roughened, sunless, cruel, nonaristocratic, intemperate, clangorous, savage, common, rugged, overcast, hateful, gloomy, low, mean, hard, unlovely, dogged, blaring, ignoble, tyrannical, ill-humored, crusty, crashing, bleak, unamiable, violent, plebeian, gusty, rip-roaring, rude, steep, degraded, exquisite, blasting, cloudy, heavy, windy, harsh, clarion, dinning, dirty, overloud, roaring, showery, gruff, surly, sullen, nasty, unkind, roughening, baseborn, raw, churlish, bastard, wild, dismal, junior, hazy, heavy-handed, sour, coarse, vociferous, gray, ungentle, pitiless, inclement, plangent, illegitimate, trumpetlike, humble, subordinate, oppressive, fierce, sonorous, loud, severe.
Usage samples:
  1. He was sorry for him and very gentle.
    "A Journal of Impressions in Belgium", May Sinclair.
  2. " Ah, possibly," said Saya Chone; " but then for my purpose the soft voice, the gentle whisper, was the only thing."
    "Jack Haydon's Quest", John Finnemore.
  3. A faint smile crept over Agnes' lips, but she checked it in an instant, and moved forward with an air of gentle interest.
    "Mabel's Mistake", Ann S. Stephens.
  4. To think that made her very gentle and, I believe, brought her a kind of light.
    "My Little Sister", Elizabeth Robins.