Most Powerful Dua against Enemy

اَللَّهُمَّ مُنْزِلَ الْكِتَابِ، وَمُجْرِيَ السَّحَابِ، وَهَازِمَ الْأَحْزَابِ، اِهْزِمْهُمْ وَانْصُرْنَا عَلَيْهِمْ.

Transliteration

Allaahumma munzilal kitaab, wa muj’riyas sahaab wa haazimal ahzaab, ihzimhum wansurnaa alayhim.

Meaning

O Allah! The Revealer of the (Holy) Book, the Mover of the clouds, and Defeater of Al-Ahzab (i.e. the clans of infidels), defeat them infidels and bestow victory upon us.

Source: Bukhari: 2966