| sheer(adjective, severe, difficult, cold, complex) |
| troublesome(adjective, tough, evil, difficulty, rough) |
| cold-blooded(adjective, person, mean, cool, tough) |
| hardened(adjective, tough, severe, firm, attitude) |
| ruthless(adjective, mean, tough, severe, evil) |
| strenuous(adjective, dull, great, tough, severe) |
| uncompromising(adjective, mean, severe, rough, difficult) |
| unkind(adjective, person, mean, cool, tough) |
| exacting(adjective, dull, tough, easy, severe) |
| hardhearted(adjective, person, mean, severe, attitude) |
| obstinate(adjective, mean, tough, rough, harsh) |
| unbending(adjective, mean, strong, tough, severe) |
| unrelenting(adjective, mean, strong, tough, severe) |
| impenetrable(adjective, characteristic, tough, firm, solid) |
| pitiless(adjective, mean, tough, severe, nasty) |
| unfriendly(adjective, person, mean, evil, rough) |
| cool(adjective, person, mean, unpleasant, cold) |
| formidable(adjective, tough, severe, evil, difficulty) |
| heavy(adjective, person, dull, body, strong) |
| inexorable(adjective, mean, strong, tough, severe) |