incorrigible

Defective and impossible to materially correct or set aright.

The construction flaw is incorrigible; any attempt to amend it would cause a complete collapse.

Unmanageable; impervious to correction by punishment or pain.

an incorrigible youth

Incurably depraved; not reformable.

His dark soul was too incorrigible to repent, even at his execution.

Unchangeably established in a belief or habit.

Gordon Brown may have his grumpy, Granita moments, but as a strategist he is an incorrigible optimist.

Intrinsically incapable of being corrected; impossible to disprove, by its very nature.

The statement "My knee hurts" is incorrigible.

An incorrigibly bad individual.

The incorrigibles in the prison population are either lifers or habitual reoffenders.