ferocious, fierce, grim, savage, vicious

argumentative, assaultive, bellicose, belligerent, brawly, chippy, combative, confrontational, discordant, disputatious, feisty, gladiatorial, militant, pugnacious, scrappy, warlike

bare-knuckle (also bare-knuckled or bare-knuckles), blood-and-guts, in-your-face, take-no-prisoners

contentious, quarrelsome, truculent

menacing, threatening

bestial, brute, inhuman, inhumane

barbaric, uncivilized, wild

heartless, implacable, merciless, pitiless, relentless, ruthless, unrelenting, wanton

bloodthirsty, bloody, homicidal, murdering, murderous, sanguinary, sanguine

rapacious, ravenous, voracious

amicable, companionable, comradely, congenial, cordial, friendly, genial, hearty, warm, warmhearted

compliant, submissive, tame

benign, compassionate, kind, merciful

pacific, peaceable, peaceful

amiable, complaisant, obliging

human, humane

civilized, cultured

gentle, mild, unaggressive