The postal strike has had disastrous effects on the mail-order business.
Advanced English Dictionary
+adjective very bad, harmful or unsuccessful: a disastrous harvest / fire / result + Lowering interest rates could have disastrous consequences for the economy. + It was a disastrous start to the season for the team. disastrously adverb: How could everything go so disastrously wrong?
Collocation Dictionary adj
be, prove | become
absolutely, quite, utterly
The policy was absolutely disastrous for the economy.