| Solution | Length | |
|---|---|---|
| 5 letters | ||
| tough | 5 | |
| stern | 5 | |
| stiff | 5 | |
| rigid | 5 | |
| 6 letters | ||
| misers | 6 | |
| stingy | 6 | |
| steely | 6 | |
| 7 letters | ||
| sparing | 7 | |
| unmoved | 7 | |
| 8 letters | ||
| rigorous | 8 | |
| stubborn | 8 | |
| 9 letters | ||
| unbending | 9 | |
| unpliable | 9 | |
| 10 letters | ||
| relentless | 10 | |
| UNGENEROUS | 10 | |
| UNYIELDING | 10 | |
| UNAFFECTED | 10 | |
| 11 letters | ||
| unalterable | 11 | |
| unrelenting | 11 | |
| 12 letters | ||
| UNCHANGEABLE | 12 | |
| 14 letters | ||
| UNCOMPROMISING | 14 | |