| flinty(adjective, strong, hard, tough, severe) |
| frigid(adjective, mean, hard, harsh, cold) |
| hard-core(adjective, strong, hard, tough, severe) |
| hardened(adjective, hard, tough, harsh, cruel) |
| immutable(hard, resolute, rigid, inflexible, strict) |
| indefatigable(adjective, resolute) |
| indifferent(adjective, mean, hard, harsh, cold) |
| indomitable(adjective, set, strong, hard, tough) |
| insensitive(adjective, hard, tough, harsh, cruel) |
| insistent(adjective, resolute) |
| opinionated(adjective, determined, resolute, uncompromising, unshakeable) |
| pat(adjective, determined, resolute, uncompromising, unshakeable) |
| persevering(adjective, resolute) |
| punitive(adjective, severe, harsh, cruel, reactive) |
| sadistic(adjective, mean, evil, nasty, harsh) |
| self-opinionated(adjective, determined, resolute, uncompromising, unshakeable) |
| serious(adjective, strong, hard, tough, severe) |
| single-minded(adjective, tough, firm, harsh, cruel) |
| staunch(adjective, hard, firm, determined, resolute) |
| steady(adjective, resolute) |