| never-say-die |
| overpowering(adjective, strong, great, strength, tough) |
| patient(adjective, calm, strong, cool, firm) |
| pertinacious(adjective, strong, tough, firm, difficult) |
| refractory(difficult, wild, awkward, persistent, obstinate) |
| rigid(adjective, strong, hard, tough, persistent) |
| set(adjective, hard, resolute, persistent, obstinate) |
| single-minded(adjective, hard, resolute, persistent, obstinate) |
| strong-minded(adjective, determined, resolution, fixed, courage) |
| strong-willed(adjective, vigorous, noble, resolution, resolute) |
| uncompromising(adjective, hard, tough, difficult, resolute) |
| unruly(difficult, wild, awkward, persistent, obstinate) |
| unswerving(adjective, strong, firm, determined, steady) |
| unwearied(adjective, strong, firm, determined, steady) |
| bullheaded(adjective, strong, hard, tough, difficult) |
| continuing(adjective, strong, firm, determined, steady) |
| decisive(adjective, resolute, tenacious) |
| devoted(adjective, strong, firm, determined, steady) |
| doughty(adjective, strong, powerful, bold, courage) |
| gritty(adjective, strong, tough, noble, resolution) |