| pitiless(adjective, harsh, cruel, determined, fierce) |
| relentless(adjective, strong, hard, tough, severe) |
| remorseless(adjective, harsh, cruel, determined, fierce) |
| rigid(adjective, strong, hard, tough, harsh) |
| rigorous(adjective, strong, hard, tough, harsh) |
| rough(adjective, strong, hard, tough, severe) |
| ruthless(adjective, harsh, cruel, determined, fierce) |
| serious(adjective, strong, hard, tough, severe) |
| severe(adjective, strong, hard, tough, harsh) |
| single-minded(adjective, harsh, cruel, determined, fierce) |
| steely(adjective, strong, hard, tough, severe) |
| stiff(adjective, harsh, cruel, determined, fierce) |
| stiff-necked(adjective, strong, hard, tough, severe) |
| stop at nothing(expression, adjective, idiom, harsh, cruel) |
| strict(adjective, strong, hard, tough, harsh) |
| stringent(adjective, harsh, cruel, determined, fierce) |
| unappeasable(adjective, harsh, cruel, determined, fierce) |
| unbending(adjective, strong, hard, tough, harsh) |
| uncompromising(adjective, severe, harsh, cruel, determined) |
| undeviating(adjective, harsh, cruel, determined, fierce) |