| persevering(adjective, resolute) |
| pig-headed(adjective, determined, resolute, obstinate, stubborn) |
| pitiless(adjective, severe, harsh, cruel, determined) |
| puritanical(adjective, severe) |
| refractory(adjective, tough, firm, difficult, violent) |
| rugged(adjective, difficult, harsh, rigorous) |
| unflinching(adjective, firm, harsh, cruel, determined) |
| bovine(adjective, determined, resolute, obstinate, unshakeable) |
| brass-bound(adjective, determined, resolute, obstinate, unshakeable) |
| hard-core(adjective, severe, firm, harsh, stubborn) |
| indurate(adjective, mean, hard, determined, resolute) |
| iron-willed(adjective, determined, resolute, unshakeable) |
| resistant(adjective, determined, resolute, obstinate, unshakeable) |
| rock-ribbed(adjective, determined, resolute, unshakeable) |
| stalwart |
| steady(adjective, clear, firm, certain, definite) |
| strait-laced(adjective, severe, severity) |
| unsympathetic(adjective, mean, hard, severe, harsh) |
| willful(adjective, tough, firm, determined, resolute) |
| authoritarian(adjective, severe) |