merciless

adj.

[1]

unmerciful , cruel , pitiless , ruthless , heartless , unmerciful , inhumane , inhuman , brutal , savage , barbarous , barbaric , barbarian , crude , rude , rough , harsh , tough , callous , hard , hard-hearted , illiberal , tyrannical , stony-hearted , cold , severe , unsparing , insensitive , indifferent , unsympathetic , unforgiving , ungracious , malevolent , thoughtless , uncharitable , inconsiderate , unmoved , unbending , inflexible , relentless , unrelenting , inexorable