| ingrained(adjective, continue, confirmed) |
| intractable(adjective, determined, persistent, impulsive, obstinate) |
| refractory(adjective, determined, persistent, impulsive, obstinate) |
| settled(adjective, continue, confirmed) |
| strict(adjective, strong, hard, tough, severe) |
| ungovernable(adjective, determined, persistent, impulsive, obstinate) |
| unruly(adjective, determined, persistent, impulsive, obstinate) |
| accepted(adjective, confirmed) |
| accustomed(adjective, confirmed) |
| adamant(adjective, strong, hard, tough, sturdy) |
| anal-retentive(adjective, persistent, obstinate, insistent, dogged) |
| astringent(adjective, strong, hard, tough, severe) |
| austere(adjective, strong, hard, tough, severe) |
| authoritarian(adjective, strong, hard, tough, severe) |
| 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) |
| cantankerous(adjective, persistent, obstinate, insistent, dogged) |
| chronic(adjective, confirmed) |