Steel-hearted is a term used to describe someone as being harsh or unfeeling in their emotions or actions. There are many synonyms that can be used to describe someone who is steel-hearted such as stoic, unemotional, callous, hard-hearted, unfeeling, tough-minded, unsympathetic, indifferent, cold-blooded, uncompassionate, and cold-hearted.
These terms all convey a sense of emotional detachment, hardness, or cruelty. Steel-hearted individuals are often seen as being unapproachable or inaccessible to others because of their lack of compassion. These synonyms provide a variety of ways to describe someone who is steel-hearted, but all suggest that this person is not easily swayed by emotions or concerned with the feelings of others.