Fear the Oppressed [Du’aas Against Enemy Included] (Hadith No. 2125)

Bismillah.

Volume 3, Book 43, Number 628:
Narrated Ibn ‘Abbas (radiallaahu `anhu):
The Prophet (sallallaahu `alayhi wasallam) sent Mu’adh to Yemen and said, “Be afraid, from the curse of the oppressed as there is no screen between his invocation and Allah.”

That simply means that if he asks Allah to destroy the oppressor in the worst way possible, Allah might be very quick to accept his dua. So be afraid!

“Oh Allah! We put You in front of them, and we seek refuge in You from their evils!”