| inflexible(adjective, strong, hard, tough, severe) |
| stern(adjective, serious, authoritarian) |
| callous(adjective, evil, nasty, harsh, vicious) |
| granitic |
| heartless(adjective, evil, nasty, harsh, vicious) |
| pitiless(adjective, close, hard, severe, nasty) |
| ruthless(adjective, evil, nasty, harsh, cruel) |
| unbending(adjective, close, strong, hard, tough) |
| grim(adjective, close, strong, hard, tough) |
| hard-hearted(adjective, evil, nasty, harsh, vicious) |
| merciless(adjective, evil, nasty, harsh, vicious) |
| relentless(adjective, close, strong, hard, tough) |
| stiff(adjective, strong, hard, severe, harsh) |
| unkind(adjective, evil, nasty, harsh, vicious) |
| brutal(adjective, evil, nasty, harsh, cruel) |
| hardened(adjective, rocky, pebbly) |
| mean(adjective, nasty, unkind, pitiless, malicious) |
| rigorous(adjective, strong, hard, tough, severe) |
| rocklike |
| solid |