He had a catastrophic defeat.

A. improbable

B. disastrous

C. revolutionary

D. pessimistic

Answer: Option B

Solution(By Examveda Team)

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