| labyrinthine(adjective, hard, difficulty, difficult, complex) |
| massive(adjective, hard, difficult, complex) |
| nasty(adjective, hard, severe, rough, difficult) |
| sensitive(adjective, hard, difficult, delicate, uncertain) |
| serious(adjective, strong, hard, tough, difficult) |
| stubborn(adjective, strong, hard, tough, difficulty) |
| toilful(adjective, hard, difficult, complex, awkward) |
| dire(adjective, hard, difficult, unpleasant, complex) |
| hardy(adjective, strong, sound, tough, continue) |
| painful(adjective, hard, tough, difficult, harsh) |
| punishing(adjective, hard, difficult, complex) |
| uneven(adjective, mean, hard, smooth, severe) |
| powerful(adjective, strong, sound, tough, fit) |
| craggy(adjective, hard, smooth, severe, sharp) |
| hale(adjective, strong, sound, tough, fit) |
| husky(adjective, strong, tough, big, coarse) |
| muscular(adjective, strong, sound, tough, fit) |
| rocky(adjective, rough, harsh, delicate, uncertain) |
| healthy(adjective, strong, tough, fit, intense) |
| jagged(adjective, mean, hard, smooth, severe) |