One who cannot be cured.
Irremediable, incorrigible.
Of an illness, condition, etc, that is unable to be cured; healless.
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.