6627. He had a catastrophic defeat.

✅ The correct answer is option B.
Improbable : not likely to be true or to happen.

Disastrous : causing great damage.

Revolutionary : involving or causing a complete or dramatic change.

Pessimistic : tending to see the worst aspect of things or believe that the worst will happen.

Catastrophic : extremely unfortunate or unsuccessful.

Synonym of Catastrophic is Disastrous