| hard(adjective, mean, harsh, cruel, vicious) |
| hard-boiled(adjective, tough, rigid, scrupulous) |
| hard-headed(adjective, persistent, constant, prearranged, dogged) |
| hard-nosed(adjective, cruel, stiff, brutal, strict) |
| hardboiled(adjective, prearranged, dogged, unabated) |
| hardhearted(adjective, cruel, brutal, pitiless, callous) |
| harsh(adjective, mean, cruel, vicious, brutal) |
| hatchet job(expression, adjective, unsparing, inhumane) |
| having a killer instinct(expression, adjective, idiom, unsparing, inhumane) |
| in the groove(adjective, disciplined, structured) |
| incessant(adjective, persistent, constant) |
| inflexible(adjective, cruel, pitiless, merciless, ruthless) |
| inhumane(adjective, unsparing) |
| intractable(adjective, cruel, pitiless, merciless, ruthless) |
| intransigent(adjective, persistent, constant) |
| iron-fisted(adjective, dogged, disciplined, structured, unsparing) |
| ironclad(adjective, stiff, strict, demanding) |
| mean machine(expression, adjective, unsparing, inhumane) |
| miser |
| no-nonsense(adjective, tough, rigid, scrupulous) |