Synonyms for callous

unfeeling, insensitive, inured, hardened, unsusceptible, uncaring, unaffected by, hard, insensible, stubborn, stiff, unbending, indurated, obdurate, insentient, insensate, inflexible, cold, coldhearted, hardhearted, unresponsive, unconcerned, impassive, apathetic, heartless, coldblooded, impenitent, unsympathetic, soulless, spiritless, toughened, blind to, deaf to, unimpressionable, tough*, hard-boiled*, thick-skinned*, case-hardened*, hard as nails*; see also cruel 2, indifferent 1.

Antonyms concerned, compassionate, sensitive.