| immovable |
| impenetrable(adjective, hard, unfeeling, unsympathetic, prepared) |
| imperceptive(adjective, hard, indifferent, unkind, unresponsive) |
| impious(adjective, hard, unfeeling, unsympathetic, prepared) |
| implacable(adjective, mean, hard, severe, harsh) |
| inaccessible(adjective, hard, unfeeling, unsympathetic, prepared) |
| incurious(adjective, hard, indifferent, unkind, unresponsive) |
| indurated(adjective, hard, unfeeling, unsympathetic, hardened) |
| inexorable(adjective, mean, hard, harsh, cold) |
| inflexible(adjective, hard, unfeeling, unsympathetic, response) |
| insensible(adjective, dull, mean, hard, slow) |
| inured(adjective, hard, unfeeling, unsympathetic, hardened) |
| ironhearted |
| irreverent(adjective, hard, unfeeling, unsympathetic, prepared) |
| killer instinct(expression, adjective, mean, hard, harsh) |
| laid-back(adjective, detached, impassive, unresponsive, reticent) |
| listless(adjective, dull, slow, detached, unfeeling) |
| lone wolf(adjective, person) |
| marble(adjective, detached, impassive, unresponsive, insensitive) |
| not responsive(expression, adjective, detached, impassive, unresponsive) |