| unrelenting(adjective, strong, tough, cold, determined) |
| willful(adjective, strong, tough, firm, difficult) |
| business-minded |
| uncompromising(adjective, tough, firm, determined, resolute) |
| contumacious(adjective, tough, firm, determined, unreasonable) |
| opinionated(adjective, tough, firm, determined, resolute) |
| relentless(adjective, strong, tough, firm, energetic) |
| hard-nosed(adjective, determined, resolute, obstinate, uncompromising) |
| indefatigable(adjective, strong, firm, determined, steady) |
| insistent(adjective, determined, resolute, obstinate, uncompromising) |
| persevering(adjective, strong, tough, firm, determined) |
| perverse(adjective, tough, firm, resist, determined) |
| refractory(adjective, tough, firm, difficult, determined) |
| rigid(adjective, tough, determined, resolute, obstinate) |
| stiff-necked(adjective, tough, firm, resist, determined) |
| untiring(adjective, determined, persevering) |
| unwavering(adjective, strong, firm, determined, steady) |
| deaf(adjective, stubborn, unwilling) |
| diligent(adjective, persevering) |
| tireless(adjective, strong, firm, energetic, determined) |