| grasping(adjective, anxious, attentive, greedy, resentful) |
| grievous(adjective, hard, tough, difficult, harsh) |
| grinding(adjective, rough, difficult, harsh, heavy) |
| grueling(adjective, hard, tough, severe, difficult) |
| gruff(adjective, severe) |
| hairy(adjective, hard, tough, severe, rough) |
| herculean(adjective, tough, severe, rough, difficult) |
| incumbent |
| inexorable(adjective, persistent, obstinate, insistent, dogged) |
| inquiring(verb, requesting) |
| insatiable(avid, greedy, voracious) |
| intricate(adjective, hard, tough, severe, difficult) |
| inviting(verb, requesting) |
| irascible(adjective, keen, violent, anxious, eager) |
| irritable(adjective, tough, severe, keen, cross) |
| irritating(adjective, dull, tough, severe, boring) |
| literal(adjective, fastidious) |
| merciless(adjective, tough, severe, rough, difficult) |
| no picnic(expression, hard, tough, severe, rough) |
| not easy(expression, tough, severe, painful, problematic) |