uncompassionate (adj.)

• bowelless
• callous
• coldhearted
• cruel
• disagreeable
• flinty
• hard
• hard-boiled
• hardhearted
• harsh
• heartless
• ill
• inclement
• inexorable
• inhospitable
• merciless
• obdurate
• pitiless
• relentless
• remorseless
• ruthless
• unaffectionate
• uncordial
• unemotional
• unfeeling
• unforgiving
• ungracious
• unkind
• unkindly
• unloving
• unmerciful
• unpitying
• unremorseful
• unsympathetic
• unsympathizing
• unyielding