| pertinacious(adjective, tough, determined, resolute, obstinate) |
| perverse(adjective, mean, hard, tough, deliberate) |
| steely(adjective, strong, hard, tough, resolute) |
| refractory(adjective, tough, firm, determined, unreasonable) |
| severe(adjective, mean, strong, hard, tough) |
| unforgiving(adjective, person, mean, hard, rough) |
| unmoved(adjective, cold, indifferent, determined, fixed) |
| hardened(adjective, person, feelings, determined, resolute) |
| pat(adjective, determined, resolute, obstinate, unyielding) |
| persistent(adjective, strong, tough, flat, firm) |
| rigorous(adjective, strong, hard, tough, harsh) |
| stiff-necked(adjective, mean, strong, hard, tough) |
| strict(adjective, strong, hard, tough, flat) |
| business-minded |
| contrary(adjective, determined, fixed, resolute, persistent) |
| decided(adjective, determined, resolute, uncompromising, unshakeable) |
| diamond(noun, jewel, rock, mineral, gem) |
| harsh(adjective, mean, strong, hard, tough) |
| opinionated(adjective, tough, firm, determined, resolute) |
| recalcitrant(adjective, tough, firm, unreasonable, grim) |