| hardheaded(adjective, determined, resolute, uncompromising, unshakeable) |
| hardhearted(adjective, mean, severe, harsh, cruel) |
| hatchet job(expression, adjective, mean, severe, harsh) |
| having a killer instinct(expression, adjective, idiom, mean, severe) |
| heartless(adjective, mean, severe, harsh, cruel) |
| immovable(adjective, determined, resolute, uncompromising, unshakeable) |
| incontrollable |
| inconvincible(adjective, determined, resolute, uncompromising, unshakeable) |
| inhuman(adjective, mean, harsh, cruel, determined) |
| inhumane(adjective, mean, severe, harsh, cruel) |
| insistent(adjective, persistent, avid, greedy, unyielding) |
| insuppressible |
| intractable(adjective, cruel, pitiless, merciless, ruthless) |
| iron-fisted(adjective, mean, severe, harsh, cruel) |
| ironfisted(adjective, mean, severe, harsh, cruel) |
| irrepressible |
| mean(adjective, severe, harsh, cruel, vicious) |
| mean machine(expression, adjective, mean, severe, harsh) |
| mercenary |
| miserly |