| indomitable(adjective, strong, firm, determined, steady) |
| set(adjective, strong, hard, tough, firm) |
| single-minded(adjective, tough, firm, harsh, solid) |
| strong-willed(adjective, strong, tough, firm, determined) |
| diligent(adjective, resolute, tenacious) |
| hardheaded(adjective, tough, firm, resist, determined) |
| perseverant(adjective, determined, persistent) |
| unswerving(adjective, strong, tough, firm, solid) |
| willful(adjective, tough, firm, resist, determined) |
| decided(adjective, strong, firm, serious, resolute) |
| dedicated(adjective, feature, characteristic, strong, firm) |
| fixed(adjective, mean, hard, tough, firm) |
| grim(adjective, appearance, tough, harsh, cruel) |
| purposeful(adjective, feature, characteristic, strong, tough) |
| stiff(adjective, set, harsh, cruel, determined) |
| stiff-necked(adjective, mean, hard, tough, firm) |
| unflinching(adjective, strong, firm, harsh, energetic) |
| bold(adjective, resolute, tenacious) |
| implacable(adjective, appearance, mean, hard, tough) |
| opinionated(adjective, tough, firm, determined, resolute) |