| difficult(adjective, hard, tough, rough, heavy) |
| demanding(adjective, tough, severe, rough, difficult) |
| arduous(adjective, tough, severe, rough, difficult) |
| critical |
| exacting(adjective, tough, severe, rough, difficult) |
| formidable(adjective, tough, severe, rough, difficult) |
| hairy(adjective, tough, rough, difficult, heavy) |
| hard(adjective, difficult, awkward, demanding, grueling) |
| intricate(adjective, tough, severe, rough, difficult) |
| knotty(adjective, tough, rough, difficult, heavy) |
| laborious(adjective, tough, severe, rough, difficult) |
| mean(adjective, tough, rough, difficult, heavy) |
| not easy(expression, adjective, tough, severe, painful) |
| operose(adjective, tough, severe, rough, difficult) |
| rigorous(adjective, tough, rough, difficult, heavy) |
| rough(adjective, tough, difficult, heavy, awkward) |
| rugged(adjective, tough, rough, difficult, heavy) |
| severe(adjective, tough, rough, difficult, heavy) |
| titanic(adjective, tough, severe, painful, problematic) |
| toilsome(adjective, tough, severe, rough, difficult) |