Similar word to iron-hearted:

anesthetized, apathetic, asleep, benumbed, brutal, callous, cantankerous, churlish, cold, cold fish, cold-blooded, cold-hearted, crotchety, cruel, deadened, exacting, feelingless, hard, hardened, heartless, icy, inanimate, inhuman, insensate, insensible, insensitive, ir