| inevitable(certain, unquestionable, undisputable) |
| inexhaustible |
| inexorable(adjective, intense, resolute, persistent, rigid) |
| infallible(adjective, certain, flawless, reliable, trustworthy) |
| infernal(adjective, complete, total, definite, absolute) |
| inflexible(adjective, strong, flat, certain, determined) |
| intense(adjective, firm, solid, steady, stable) |
| intent(adjective, strong, flat, certain, determined) |
| invariable |
| inveterate(adjective, certain, limited, definite, inflexible) |
| lasting |
| level(adjective, certain, limited, definite, inflexible) |
| levelheaded(adjective, firm, solid, stable, fixed) |
| limited(adjective, certain, definite, inflexible, restricted) |
| loyal(adjective, firm, solid, intense, certain) |
| narrow(adjective, certain, limited, definite, inflexible) |
| no catch(expression, adjective, complete, total, definite) |
| no ifs ands or buts(expression, adjective, idiom, complete, total) |
| obdurate(adjective, strong, flat, intense, certain) |
| perfect(adjective, complete, total, definite, safe) |