| stiff(adjective, strong, hard, tough, severe) |
| unrelenting(adjective, firm, determined, rigid, obstinate) |
| unshakable(adjective, determined, obstinate, uncompromising, unshakeable) |
| adamant(adjective, strong, hard, secure, tough) |
| courageous(adjective, clear, strong, tough, severe) |
| tenacious(adjective, clear, strong, tough, severe) |
| dogged(adjective, appearance, strong, tough, firm) |
| persistent(adjective, strong, tough, flat, firm) |
| staunch(noun, adjective, calm, close, clear) |
| brave(adjective, clear, strong, tough, severe) |
| unbendable(adjective, determined, obstinate, uncompromising, unshakeable) |
| decided(adjective, set, firm, intense, deliberate) |
| persevering(adjective, strong, tough, keen, flat) |
| unfaltering(adjective, strong, firm, solid, intense) |
| loyal(adjective, close, correct, keen, firm) |
| unflinching(adjective, strong, flat, firm, certain) |
| hard-nosed(adjective, determined, obstinate, uncompromising, unshakeable) |
| steady(adjective, calm, close, strong, secure) |
| tough(adjective, calm, clear, strong, hard) |
| pertinacious(adjective, strong, tough, firm, determined) |