incorrigible
adjective
°defective and impossible to materially correct or set aright.
"''The construction flaw is incorrigible; any attempt to amend it would cause a complete collapse."
°incurably depraved; not reformable.
"''His black soul was too incorrigible to repent, even at his execution."
noun
°An incorrigibly bad individual.
"''The incorrigibles in the prison population are either lifers or habitual reoffenders"
synonyms: irredeemable, irreparable