An incorrigibly bad individual.
Unmanageable.
Defective and impossible to materially correct or set aright.
Impervious to correction by punishment or pain.
Determined, unalterable, hence impossible to improve upon.
Incurably depraved; not reformable.
Someone suicidal; someone likely to kill themselves.
Likely to commit, or to attempt to commit, suicide.
Extremely reckless.
Highly likely to certain to result in the deaths of the participants; dangerous or reckless to such a degree as to be tantamount to suicide for those taking part.
Pertaining to suicide.