| disturbing(adjective, hard, difficult, complex) |
| hard to understand(expression, adjective, idiom, hard, difficult) |
| impossible(adjective, hard, difficulty, difficult, complex) |
| multiplex(adjective, hard, difficult, complex) |
| oppressive(adjective, hard, difficult, complex, demanding) |
| painful(adjective, hard, difficult, complex) |
| serious(adjective, hard, difficult, complex, awkward) |
| abstruse(noun, adjective, hard, fancy, evil) |
| grinding(adjective, hard, difficult, complex, awkward) |
| messy(adjective, hard, difficult, complex) |
| multiple(adjective, hard, difficult, complex) |
| precarious(adjective, hard, difficult, complex) |
| sheer(adjective, hard, fancy, difficult, delicate) |
| stubborn(adjective, hard, difficulty, difficult, complex) |
| toilful(adjective, hard, difficult, complex, awkward) |
| tangled(adjective, hard, simple, obscure, difficulty) |
| ornate(adjective, fancy, delicate, complex, special) |
| convoluted(adjective, hard, simple, fancy, obscure) |
| obscure(adjective, hard, difficult, heavy, complex) |
| perplexing(adjective, hard, fancy, obscure, difficult) |