Callous (adjective)

1. Having or showing an insensitive and cruel disregard for others.
2. Having calluses.
3. Hardened, unfeeling.

Origin:

Early 15c., from middle french calloux, from latin callosus "hard, horny," from callum (genitive calli) "callus, hard skin," of uncertain origin.

Examples:

1. The callous criminal showed no remorse for his actions.
2. She was callous about the plight of the refugees.
3. His callous attitude towards the suffering of others was reprehensible.
4. I had to develop callous on my fingers from playing the guitar so much.
5. He had callous on his feet from standing for long hours.