| grueling(adjective, tough, severe, difficult, harsh) |
| gruff(adjective, severe) |
| hairy(adjective, hard, tough, severe, rough) |
| hard-boiled(adjective, hard, tough, severe, rough) |
| hard-hearted(adjective, hard, tough, severe, cold) |
| hard-line(adjective, persistent, obstinate, insistent, dogged) |
| hard-shell(adjective, persistent, severity, obstinate, insistent) |
| herculean(adjective, tough, severe, rough, difficult) |
| high(adjective, unreasonable, extravagant, ridiculous, excessive) |
| icy(adjective, hard, tough, severe, cold) |
| immoderate(adjective, unreasonable, extravagant, ridiculous, excessive) |
| imperious(adjective, overbearing, bossy) |
| importunate |
| inclement(adjective, hard, tough, severe, rough) |
| industrious(adjective, thorough, meticulous, painstaking) |
| inhuman(adjective, hard, tough, severe, cold) |
| inordinate(adjective, unreasonable, extravagant, ridiculous, excessive) |
| intolerant(adjective, severe) |
| knotty(adjective, hard, tough, severe, rough) |
| literal(adjective, fastidious) |