| decisive(adjective, resolute) |
| exacting(adjective, tough, easy, severe, painful) |
| fractious(adjective, tough, unpleasant, deliberate, determined) |
| froward(adjective, cross, deliberate, determined, impulsive) |
| hard-hearted(adjective, mean, hard, tough, harsh) |
| immutable(adjective, hard, firm, steady, fixed) |
| irreconcilable(adjective, unwilling) |
| reliable(adjective, resolute, persistent, dedicated, unwavering) |
| reluctant(adjective, unwilling) |
| rocklike(adjective, hard, firm, stiff, compact) |
| rocky(adjective, firm, difficult, stiff, rigid) |
| stanch |
| stark(adjective, strong, hard, sound, tough) |
| sure(adjective, strong, tough, flat, firm) |
| tense(adjective, hard, firm, solid, stiff) |
| tireless(adjective, resolute) |
| unapologetic |
| unbeatable |
| uncontrollable(adjective, determined, impulsive, stubborn, reckless) |
| ungiving(adjective, firm) |