| strong(adjective, hard, tough, sturdy, rigid) |
| strong-willed(adjective, determined, resolute, uncompromising, unshakeable) |
| unbreakable(adjective, firm, rigid, unyielding) |
| unchangeable(adjective, set, hard, stiff, resolute) |
| unmoved(adjective, cold, cruel, unfeeling, unsympathetic) |
| austere(adjective, strong, hard, tough, severe) |
| cold-blooded(adjective, cold, cruel, unfeeling, unsympathetic) |
| cool |
| dour |
| gray(dull, leaden) |
| grim(adjective, dull, strong, hard, tough) |
| hardened(adjective, hard, firm, solid, cold) |
| icy(adjective, aloof) |
| inelastic(adjective, hard, firm, solid, stiff) |
| insensitive(adjective, unfeeling, unsympathetic, pitiless, hardhearted) |
| pitiless(adjective, cold, cruel, unfeeling, unsympathetic) |
| resolved(adjective, determined, resolute, uncompromising, unshakeable) |
| ruthless(adjective, cold, cruel, resolute, unfeeling) |
| solid(adjective, hard, firm, stiff, tense) |
| staunch(adjective, set, hard, stiff, resolute) |