| stubborn(adjective, hard, complex, change, position) |
| taxing(adjective, hard, tough, rough, harsh) |
| rugged(adjective, hard, severe, evil, rough) |
| profound(adjective, hard, complex, thoughtful, intellectual) |
| serious(adjective, hard, tough, easy, harsh) |
| stressful(adjective, hard, complex) |
| grievous(adjective, hard, complex, sickness, ache) |
| oppressive(adjective, dull, hard, tough, severe) |
| sticky(adjective, hard, delicate, complex, awkward) |
| operose(adjective, hard, tough, severe, difficulty) |
| tight(adjective, hard, complex) |
| weighty(adjective, hard, heavy, complex) |
| demanding(adjective, dull, hard, tough, severe) |
| ambitious(adjective, hard, ability, complex, effort) |
| nasty(adjective, hard, rough, rude, unpleasant) |
| precarious(adjective, hard, complex) |
| esoteric(adjective, hard, complex, complicated) |
| sore(adjective, hard, complex, sickness, ache) |
| dire(adjective, hard, complex, sickness, ache) |
| backbreaking(adjective, hard, heavy, complex, awkward) |