| austere(adjective, strong, hard, tough, severe) |
| authoritarian(adjective, strong, hard, tough, severe) |
| awkward(tough, difficult, wild, obstinate, stubborn) |
| bitter(adjective, strong, hard, tough, severe) |
| bloody-minded(adjective, persistent, obstinate, insistent, dogged) |
| bullheaded(adjective, strong, hard, tough, severe) |
| by the book(expression, adjective, idiom, strong, hard) |
| callous(adjective, hard, tough, severe, rough) |
| confirmed(adjective, persistent, obstinate, insistent, dogged) |
| contumacious(adjective, persistent, obstinate, insistent, dogged) |
| cruel(adjective, strong, hard, tough, severe) |
| cussed(adjective, persistent, obstinate, insistent, dogged) |
| defiant(adjective, persistent, obstinate, insistent, dogged) |
| demanding(adjective, persistent, obstinate, insistent, dogged) |
| determined(adjective, persistent, obstinate, insistent, dogged) |
| difficult(tough, wild, awkward, obstinate, stubborn) |
| disciplinary(adjective, strong, hard, tough, severe) |
| disobedient(adjective, persistent, obstinate, insistent, dogged) |
| dyed-in-the-wool(adjective, strong, hard, tough, severe) |
| flinty(adjective, strong, hard, tough, severe) |