| Solution | Length | |
|---|---|---|
| 5 letters | ||
| tough | 5 | |
| stern | 5 | |
| harsh | 5 | |
| rough | 5 | |
| 6 letters | ||
| brutal | 6 | |
| severe | 6 | |
| rugged | 6 | |
| strict | 6 | |
| 7 letters | ||
| zealous | 7 | |
| drastic | 7 | |
| profuse | 7 | |
| spartan | 7 | |
| 8 letters | ||
| vehement | 8 | |
| princely | 8 | |
| tireless | 8 | |
| original | 8 | |
| rigorous | 8 | |
| ruthless | 8 | |
| SEDULOUS | 8 | |
| 9 letters | ||
| merciless | 9 | |
| unpitying | 9 | |
| stringent | 9 | |
| UNWEARIED | 9 | |
| sleepless | 9 | |
| UNSELFISH | 9 | |
| stintless | 9 | |
| 10 letters | ||
| UNFLAGGING | 10 | |
| unmerciful | 10 | |
| ungrudging | 10 | |
| unstinting | 10 | |
| relentless | 10 | |
| 11 letters | ||
| UNREMITTING | 11 | |