| inanimate(adjective, hard, tough, severe, cold) |
| incurious(adjective, indifferent, detached, distant, remote) |
| indifferent(adjective, calm, cool, restrained, detached) |
| indurate(adjective, mean, hard, tough, harsh) |
| inexorable(adjective, mean, hard, tough, harsh) |
| inflexible(adjective, mean, hard, harsh, stubborn) |
| inhuman(adjective, hard, tough, severe, cold) |
| insensate(adjective, hard, tough, severe, cold) |
| insensible(adjective, hard, tough, severe, cold) |
| insensitive(adjective, hard, tough, severe, cold) |
| iron(adjective, mean, hard, tough, harsh) |
| iron-hearted(adjective, hard, tough, severe, cold) |
| laid-back(adjective, calm, restrained, unconcerned, subdued) |
| laid back(expression, adjective, cool, indifferent, detached) |
| lone wolf(expression, adjective, indifferent, detached, distant) |
| loner(adjective, indifferent, detached, distant, remote) |
| matter-of-fact(adjective, cool, detached, blank, sober) |
| mean(adjective, hard, tough, harsh, unfeeling) |
| merciless(adjective, hard, tough, severe, cold) |
| mulish(adjective, mean, hard, harsh, inflexible) |