| firm(adjective, tough, severe, harsh, rigid) |
| forbidding(adjective, tough, severe, firm, harsh) |
| gratuitous(adjective, mean, severe, harsh, cruel) |
| grim(adjective, mean, tough, severe, firm) |
| hanging tough(expression, adjective, persistent, constant, pitiless) |
| hard(adjective, mean, tough, severe, firm) |
| hard-boiled(adjective, tough, severe, firm, harsh) |
| hard-headed(adjective, persistent, constant, pitiless, unyielding) |
| hardhearted(adjective, mean, severe, harsh, cruel) |
| harsh(adjective, mean, tough, severe, firm) |
| hatchet job(expression, adjective, mean, severe, harsh) |
| having a killer instinct(expression, adjective, idiom, mean, severe) |
| heartless(adjective, mean, severe, harsh, cruel) |
| implacable(adjective, mean, severe, harsh, cruel) |
| incessant(adjective, persistent, constant, pitiless, unyielding) |
| inexorable(adjective, mean, severe, harsh, cruel) |
| inflexible(adjective, severe, harsh, stiff, rigid) |
| inhumane(adjective, mean, severe, harsh, cruel) |
| intransigent(adjective, persistent, constant, pitiless, unyielding) |
| ironclad(adjective, severe, harsh, stiff, rigid) |