| implacable(adjective, strong, hard, tough, harsh) |
| loyal(adjective, good, strong, firm, honest) |
| pigheaded(adjective, tough, firm, deliberate, usual) |
| proved(verb, good, strong, solid, steady) |
| proven(verb, evinced, proved, ascertained, experimented) |
| serious(adjective, set, strong, severe, firm) |
| severe(adjective, persistent, rigid, obstinate, insistent) |
| stony(adjective, tenacious) |
| strict(adjective, strong, flat, harsh, certain) |
| unchanging |
| unhesitating(adjective, resolution) |
| vigorous(adjective, strong, keen, solid, energetic) |
| assertive(adjective, aggressive) |
| bound(adjective, set, strong, tough, severe) |
| considered(verb, adjective, deliberate, planned, expected) |
| demonstrated(verb, evinced, proved, ascertained) |
| diligent(adjective, resolute, tenacious) |
| distinct(adjective, firm, energetic, definite, absolute) |
| emphatic(adjective, complete, warm, total, passionate) |
| faithful(adjective, good, strong, firm, honest) |