adjective / noun
incorrigible
in-KOR-ih-juh-bul/ɪnˈkɔːrɪdʒəbl/
Impossible or very difficult to reform or correct.
Even after repeated warnings, he remains an incorrigible practical joker.

Etymology
The pieces evoke someone who cannot be set straight: the verb for guiding or keeping straight became “correct.” Applied to character or conduct, “not correctable” means persistently bad or troublesome despite efforts to reform it.
In context
so incorrigible and ill- conditioned that neither good company nor good teaching could make any impression on him
More examples
- She's an incorrigible liar who invents another excuse whenever she's caught.
- My incorrigible optimism keeps me looking for a solution.
- The counselor refuses to dismiss any child as an incorrigible.
Forms
incorrigible · incorrigibles
incorrigibly adverb — In a way that resists correction.
incorrigibility noun — The quality of resisting reform or correction.
Similar words
- irredeemable
- Suggests someone is beyond saving, not just correcting.
- unmanageable
- Means difficult to control, not necessarily impossible to reform.