| hanging tough(expression, adjective, persistent, constant, pitiless) |
| hard-bitten |
| hard-boiled(adjective, cold, cruel, brutal, unkind) |
| hard-headed(adjective, persistent, constant, pitiless, unyielding) |
| hatchetjob(adjective, mean, hard, harsh, cold) |
| immovable(adjective, determined, resolute, uncompromising, unshakeable) |
| incessant(adjective, persistent, constant, pitiless, unyielding) |
| indifferent(adjective, mean, hard, harsh, cold) |
| insistent |
| iron-fisted(adjective, persistent, constant, pitiless, unyielding) |
| iron-willed(adjective, determined, resolute, uncompromising, unshakeable) |
| ironclad |
| ironfisted(adjective, mean, severe, harsh, cruel) |
| malevolent(adjective, mean, harsh, violent, cruel) |
| malicious(adjective, animal, mean, harsh, violent) |
| mean(adjective, animal, hard, harsh, cold) |
| nasty |
| pachydermatous |
| perpetual(adjective, persistent, constant, pitiless, unyielding) |
| persevering |