| demanding(adjective, dull, tough, easy, severe) |
| stale(adjective, difficult, complex, dry, bare) |
| austere(adjective, strong, tough, severe, rough) |
| ambitious(adjective, ability, difficult, complex, effort) |
| burly(adjective, difficult, complex) |
| grim(adjective, person, mean, strong, tough) |
| problematic(adjective, difficult, delicate, complex, tricky) |
| stony(adjective, mean, cool, tough, severe) |
| weighty(adjective, difficult, heavy, complex) |
| disturbing(adjective, mean, severe, difficult, harsh) |
| labyrinthine(adjective, difficult, complex, involved, tricky) |
| leaden(adjective, difficult, complex) |
| merciless(adjective, mean, tough, severe, evil) |
| ponderous(adjective, difficult, complex) |
| strict(adjective, strong, tough, easy, severe) |
| troubled(adjective, rough, difficult, complex, painful) |
| flinty(adjective, strong, tough, severe, evil) |
| Gordian(adjective, difficult, complex, intricate, thorny) |
| byzantine(adjective, difficult, complex, involved, complicated) |
| elaborate(adjective, difficult, complex, grand, involved) |