The Collaborative International Dictionary of English v.0.48:
Hard-hearted \Hard"-heart`ed\ (-h[aum]rt`[e^]d), a.
Unsympathetic; inexorable; cruel; pitiless. --
Hard"-heart`ed*ness, n.
[1913 Webster]
Moby Thesaurus II by Grady Ward, 1.0:
40 Moby Thesaurus words for "hardhearted":
Philistine, brazen, callous, calloused, case-hardened, cold,
cold of heart, coldblooded, coldhearted, conscienceless,
flinthearted, flinty, hard, hard of heart, hard-boiled, hardened,
heartless, impervious, indurated, insensitive, inured,
lost to shame, obdurate, pachydermatous, proof against, seared,
shameless, steeled against, steely, stony, stonyhearted,
thick-skinned, unblushing, uncompassionate, unemotional, unfeeling,
unmerciful, unnatural, unresponsive, unsympathetic