| disturbing(adjective, hard, difficult, complex) |
| esoteric(adjective, hard, difficult, complex) |
| grinding(adjective, hard, difficult, harsh, cruel) |
| hard-nosed(adjective, strong, hard, tough, severe) |
| heavy(adjective, strong, hard, great, tough) |
| intricate(adjective, hard, difficult, complex, awkward) |
| knotty(adjective, hard, difficult, complex, awkward) |
| ponderous(adjective, hard, difficult, complex) |
| rough(adjective, bad, strong, hard, tough) |
| rugged(adjective, strong, hard, tough, difficult) |
| sensitive(adjective, hard, difficult, complex) |
| sophisticated(adjective, hard, difficult, complex) |
| sticky(adjective, hard, difficult, complex, awkward) |
| toilful(adjective, hard, difficult, complex, awkward) |
| toilsome(adjective, hard, difficult, harsh, cruel) |
| vital(adjective, great, severe, importance, big) |
| hefty(adjective, hard, difficult, complex) |
| messy(adjective, hard, difficult, unpleasant, complex) |
| taxing(adjective, hard, difficult, complex) |
| tricky(adjective, hard, difficult, complex, awkward) |