That which cannot be rectified or made good

One word substitute is Irreparable.

Irreparable: (of an injury or loss) impossible to rectify or repair.
Irrevocable: not able to be changed, reversed, or recovered; final.
Irreconcilable: (of ideas or statements) so different from each other that they cannot be made compatible.
Irreplaceable: impossible to replace if lost or damaged.