| exacting(adjective, dull, tough, severe, rough) |
| forceful(adjective, action, strong, tough, smart) |
| industrious(adjective, strong, difficult, lively, determined) |
| strong(adjective, tough, difficult, energetic, powerful) |
| earnest(adjective, energetic, vigorous, zealous, thorough) |
| formidable(adjective, tough, severe, rough, difficult) |
| uphill(adjective, hard, great, tough, severe) |
| wearisome(adjective, dull, tough, severe, difficult) |
| busy(adjective, active) |
| gruelling |
| heavy(adjective, dull, tough, severe, rough) |
| intense(adjective, strong, tough, difficult, harsh) |
| lusty(adjective, strong, tough, intense, energetic) |
| persistent(adjective, energetic, zealous, perseverance) |
| rugged(adjective, action, strong, tough, severe) |
| severe(adjective, tough, rough, difficult, harsh) |
| tireless(adjective, strong, difficult, energetic, lively) |
| trying(adjective, dull, tough, severe, rough) |
| wearying(adjective, dull, difficult, awkward, boring) |
| determined(adjective, energetic, zealous) |