| unshakable(adjective, mean, hard, tough, determined) |
| implacable(adjective, appearance, mean, strong, hard) |
| obstinate(adjective, mean, hard, tough, firm) |
| grim(adjective, appearance, mean, strong, hard) |
| hard(adjective, mean, strong, tough, severe) |
| severe(adjective, appearance, mean, strong, hard) |
| remorseless(adjective, mean, tough, harsh, resist) |
| steadfast(adjective, firm, determined, steady, resolute) |
| stern(adjective, appearance, mean, severe, harsh) |
| cruel(adjective, appearance, mean, strong, hard) |
| unbendable(adjective, resist, determined, resolute, persistent) |
| iron(adjective, mean, strong, hard, tough) |
| unforgiving(adjective, mean, hard, tough, severe) |
| dogged(adjective, appearance, mean, hard, tough) |
| hard-nosed(adjective, mean, strong, hard, tough) |
| ruthless(adjective, appearance, mean, hard, tough) |
| merciless(adjective, appearance, mean, hard, tough) |
| strict(adjective, strong, hard, tough, severe) |
| harsh(adjective, mean, strong, hard, tough) |
| unappeasable(adjective, mean, severe, harsh, cruel) |