Unfeeling, a. — Webster enters it under “unfeeling”
1. Destitute of feeling; void of sensibility; insensible; insensate.
2. Without kind feelings; cruel; hard-hearted. To each his sufferings: all are men, Condemned alike to groan; The tender for another's pain, Th' unfeeling for his own. Gray. -- Un*feel"ing*ly, adv. -- Un*feel"ing*ness, n.
Shades of meaning
Fernald has no entry of its own for unfeelingness; he lists it under apathy.
Where he writes about it:
Unfeelingness, the Saxon word that should be the exact equivalent of apathy, really means more, a lack of the feeling one ought to have, a censurable hardness of heart. — from apathy