Incurably depraved; not reformable.
Unmanageable.
Defective and impossible to materially correct or set aright.
Impervious to correction by punishment or pain.
Determined, unalterable, hence impossible to improve upon.
An incorrigibly bad individual.
Not noble; ignoble; base.
Of a metal, being at the lower end of the electrochemical series, i.e. oxidising readily.
To make (someone or something) no longer noble