| pertinacious(adjective, tough, firm, determined, resolute) |
| strict(adjective, tough, firm, harsh, cruel) |
| unbending(adjective, tough, harsh, cruel, determined) |
| uncompromising(adjective, tough, firm, harsh, cruel) |
| unflagging |
| bigoted(adjective, passionate, violent, fervent, inflexible) |
| bound(adjective, harsh, intense, deliberate, cruel) |
| bound and determined(expression, adjective, idiom, harsh, cruel) |
| contumacious(adjective, tough, firm, unreasonable, grim) |
| decisive(adjective, determined, serious, resolute, persistent) |
| enduring(adjective, firm, solid, determined, steady) |
| faithful(adjective, keen, intense, enthusiastic, resolute) |
| guileless(adjective, resolute) |
| immutable(adjective, set, hard, stiff, rigid) |
| insistent |
| invincible(adjective, persistent, obstinate, insistent, dogged) |
| iron(adjective, tough, firm, unreasonable, grim) |
| loyal(adjective, keen, firm, sensible, solid) |
| mulish(adjective, tough, firm, determined, resolute) |
| narrow-minded(adjective, fervent, persistent, obstinate, zealous) |