| unfeeling(adjective, mean, hard, cool, tough) |
| headstrong(adjective, hard, tough, rough, harsh) |
| stiff-necked(adjective, strong, hard, tough, severe) |
| hard-boiled(adjective, person, strong, hard, tough) |
| hard-hearted(adjective, mean, hard, tough, severe) |
| harsh(adjective, mean, strong, hard, cool) |
| iron(adjective, strong, hard, tough, firm) |
| pertinacious(adjective, determined, resolute, obstinate, stubborn) |
| pigheaded(adjective, tough, determined, resolute, obstinate) |
| remorseless(adjective, mean, tough, harsh, resist) |
| unsympathetic(adjective, mean, hard, cool, tough) |
| heartless(adjective, mean, feeling, hard, cool) |
| steely(adjective, strong, hard, tough, cold) |
| uncompliant(adjective, resist, determined, resolute, obstinate) |
| contrary(adjective, difficult, determined, resolute, obstinate) |
| flinty(adjective, close, strong, hard, tough) |
| opinionated(adjective, tough, firm, determined, resolute) |
| persistent(adjective, strong, tough, flat, firm) |
| strong-willed(adjective, determined, resolute, uncompromising, unshakeable) |
| incompliant(adjective, resist, determined, resolute, obstinate) |