inhumane
merciless
unmerciful
atrocious
barbaric
barbarous
bestial
bloody
bowelless
brutal
brutish
coldhearted
cruel
cutthroat
dog-eat-dog
feral
ferine
ferocious
fierce
flinty
hard
hard-hearted
hardhearted
harsh
heartless
inclement
inexorable
inhuman
ironhearted
kill-crazy
malign
malignant
marblehearted
murderous
noncivilized
relentless
remorseless
ruthless
sanguinary
savage
stony
tameless
uncivilized
uncompassionate
uncompassioned
unfeeling
unforgiving
ungentle
unpitiful
icy
sullen
uncompromising
unsparing
vindictive