| hard(adjective, difficult, complex) |
| arduous(adjective, hard, difficult, complex) |
| laborious(adjective, hard, difficult, complex) |
| backbreaking(adjective, hard, difficult, complex, strenuous) |
| severe(adjective, hard, difficult, harsh, complex) |
| burdensome(adjective, hard, difficult, complex) |
| cruel(adjective, hard, difficult, harsh, complex) |
| toilsome(adjective, hard, difficult, complex) |
| operose(adjective, hard, difficult, complex) |
| painful(adjective, hard, difficult, complex) |
| trying(verb, adjective, hard, difficult, complex) |
| penal(adjective, hard, difficult, complex, punishment) |
| taxing(adjective, hard, difficult, complex) |
| tough(adjective, hard, difficult, complex) |
| difficult(adjective, hard, complex) |
| oppressive(adjective, hard, difficult, complex) |
| leaden(adjective, hard, difficult, complex) |
| tight(adjective, hard, difficult, complex, troublesome) |
| grave(adjective, hard, difficult, complex) |
| grievous(adjective, hard, difficult, complex) |