| exacting(adjective, persistent, obstinate, insistent, dogged) |
| extreme(adjective, passionate, violent, enthusiastic, fervent) |
| fanatical(adjective, fervent, rigid, inflexible, zealous) |
| fast(adjective, firm, sensible, solid, intense) |
| ferocious(adjective, harsh, cruel, determined, fierce) |
| fervent(adjective, passionate, violent, enthusiastic, zealous) |
| feverish(adjective, passionate, violent, enthusiastic, fervent) |
| fierce(adjective, harsh, cruel, determined, persistent) |
| fiery(adjective, passionate, violent, enthusiastic, fervent) |
| focused(adjective, feature, state, characteristic, determined) |
| formal(adjective, tough, firm, fixed, distant) |
| frank |
| frenzied(adjective, passionate, violent, enthusiastic, fervent) |
| go for broke(expression, adjective, idiom, harsh, cruel) |
| goal-oriented |
| grim(adjective, tough, firm, harsh, cruel) |
| hang-tough(adjective, harsh, cruel, determined, fierce) |
| hang in(expression, adjective, harsh, cruel, determined) |
| hard-and-fast(adjective, set, hard, stiff, rigid) |
| hard-as-nails(adjective, serious, resolute, persistent, unwavering) |