| immutable(adjective, set, hard, severe, rough) |
| impossible(adjective, difficulty) |
| inelastic(adjective, tough, firm, fixed, distant) |
| noncompliant |
| pitiless(adjective, cruel, fixed, rigid, inflexible) |
| resistant(adjective, secure, difficult, awkward, restless) |
| resolved(adjective, determined, fixed, persistent, obstinate) |
| single-minded(adjective, tough, firm, unreasonable, grim) |
| steadfast(adjective, determined, fixed, grim, persistent) |
| strict(adjective, hard, persistent, rigid, obstinate) |
| unalterable(adjective, hard, determined, fixed, inflexible) |
| unconquerable(adjective, persistent, obstinate, insistent, dogged) |
| unflinching(adjective, cruel, determined, fixed, resolute) |
| unsubmissive |
| wrongheaded(negative, hostile, persistent, obstinate, adverse) |
| adamantine(hard, tough, firm, unreasonable, grim) |
| awkward(adjective, difficulty, difficult, unpleasant, adverse) |
| bigoted(adjective, obstinacy) |
| bullheaded(adjective, tough, firm, indifferent, deliberate) |
| cold(adjective, strong, standoffish, formal, stuffy) |