| knotted(adjective, hard, difficulty, difficult, complex) |
| lumpish(adjective, hard, difficult, complex, ugliness) |
| robust(adjective, strong, hard, sound, tough) |
| sticky(adjective, hard, difficult, complex, awkward) |
| toilsome(adjective, hard, difficult, harsh, cruel) |
| lumpy(adjective, hard, rough, difficult, complex) |
| operose(adjective, hard, severe, difficult, violent) |
| taxing(adjective, hard, difficult, complex, rigorous) |
| cruel(adjective, strong, hard, tough, severe) |
| grinding(adjective, hard, difficult, harsh, cruel) |
| oppressive(adjective, hard, difficult, complex) |
| precarious(adjective, hard, difficult, informal, complex) |
| problematic(adjective, hard, difficult, delicate, uncertain) |
| tight(adjective, hard, difficult, complex) |
| backbreaking(adjective, hard, difficult, complex, awkward) |
| disturbing(adjective, hard, severe, difficult, unpleasant) |
| grievous(adjective, hard, tough, severe, difficult) |
| hard-nosed(adjective, strong, hard, tough, severe) |
| impossible(adjective, hard, difficulty, difficult, complex) |
| involved(adjective, hard, difficult, complex, awkward) |