| hard(adjective, reasonable, sensible, sober, stiff) |
| hard-as-nails(adjective, determined, serious, resolute, persistent) |
| hard-hearted(adjective, indifferent, detached, stiff, distant) |
| hard as nails(expression, adjective, idiom, tough, serious) |
| hardheaded(adjective, reasonable, firm, sensible, sober) |
| harsh(adjective, grim, painful, bleak) |
| inhuman(adjective, brutal, barbarous) |
| intent(adjective, serious, resolute, persistent, unwavering) |
| intractable(adjective, shrewd, astute, self-willed) |
| laid back(expression, adjective, indifferent, detached, distant) |
| mean business(expression, adjective, serious, resolute, persistent) |
| merciless(adjective, brutal, barbarous) |
| obdurate(adjective, tough, stiff, unfeeling, dogged) |
| obstinate(adjective, tough, serious, resolute, persistent) |
| on ice(expression, adjective, serious, resolute, persistent) |
| pat(adjective, serious, resolute, persistent, unwavering) |
| persevering(adjective, serious, resolute, persistent, unwavering) |
| persistent(adjective, serious, resolute, unwavering, gritty) |
| pitiless(adjective, brutal, barbarous) |
| plainspoken(adjective, reasonable, sensible, sober, practical) |