| difficult(adjective, dull, hard, tough, severe) |
| arduous(adjective, dull, hard, tough, severe) |
| hard(adjective, dull, severe, rough, difficult) |
| tough(adjective, dull, hard, difficult, harsh) |
| laborious(adjective, dull, hard, tough, severe) |
| oppressive(adjective, dull, hard, severe, rough) |
| onerous(adjective, dull, hard, tough, severe) |
| severe(adjective, hard, tough, rough, difficult) |
| taxing(adjective, hard, difficult, heavy, complex) |
| weighty(adjective, hard, difficult, heavy, complex) |
| toilsome(adjective, hard, tough, difficult, complex) |
| trying(adjective, dull, hard, tough, difficult) |
| grievous(adjective, hard, difficult, complex, painful) |
| painful(adjective, hard, difficult, complex, painful) |
| rugged(adjective, hard, severe, rough, difficult) |
| ponderous(adjective, hard, difficult, heavy, complex) |
| punishing(adjective, hard, difficult, complex, punishing) |
| sore(adjective, hard, difficult, complex, painful) |
| hefty(adjective, dull, hard, difficult, big) |
| leaden(adjective, hard, difficult, heavy, complex) |