| unfailing(adjective, continue) |
| unfaltering(adjective, strong, firm, energetic, vigorous) |
| bound and determined(expression, adjective, idiom, cruel, serious) |
| brassbound(adjective, resist, determined, resolute, persistent) |
| bullheaded(adjective, strong, hard, tough, determined) |
| committed(adjective, resolute, persistent, dedicated, unwavering) |
| contrary(adjective, determined, resolute, persistent, obstinate) |
| cutthroat(adjective, mean, strong, hard, severe) |
| dedicated(adjective, intense, resolute, persistent, steadfast) |
| die-hard(adjective, resist, determined, resolute, persistent) |
| flinty(adjective, close, strong, hard, tough) |
| hard-shell(adjective, strong, hard, tough, severe) |
| hardened(adjective, hard, tough, harsh, cold) |
| non-stop |
| pigheaded(adjective, mean, hard, tough, determined) |
| repetitive |
| round-the-clock(adjective, continue, continual) |
| stalwart |
| staunch(adjective, strong, tough, firm, determined) |
| unabated(adjective, continuous) |