Said especially of people and animals
ferocious, wild, savage, furious, enraged, raging, impetuous, untamed, angry, passionate, primitive, uncivilized, brutish, feral, animal, raving, terrible, frightening, fearsome, menacing, awful, venomous, bold, malevolent, malign, brutal, cruel, merciless, ruthless, bloodthirsty, bloody, murderous, sanguinary, truculent, aggressive, hostile, violent, monstrous, rough, grim, vicious, dangerous, frenzied, mad, insane, desperate, ravening, frantic, wrathful, irate, rabid, virulent, fanatical, bestial, tigerish, barbarous, hard*, tough*, hard-boiled*; see also sense 2.
Said especially of actions and the weather
boisterous, violent, vehement, threatening, severe, stormy, thunderous, howling, inclement, tumultuous, turbulent, uncontrolled, unbridled, unrestrained, raging, storming, blustering, cyclonic, blizzardy, torrential, of hurricane force, frightful, fearful, lowering, destructive, devastating, hellish, rip-roaring*; see also sense 1.
Showing or suggesting a disposition to be violently destructive without scruple or restraint:barbarous, bestial, cruel, fell2, feral, ferocious, inhuman, savage, truculent, vicious, wolfish. See kind
So intense as to cause extreme suffering:cruel, ferocious, savage, vicious. See help, kind
Intensely violent in sustained velocity:furious, heavy, high, strong. See strong
Extreme in degree, strength, or effect:desperate, furious, intense, terrible, vehement, violent. See big, strong
Intensely sustained, especially in activity:concentrated, heavy, heightened, intense, intensive. See strong