Prophet (ﷺ) said, If anyone fears to encounter an enemy or those of authority, then he should say:

اَللَّهُمَّ رَبَّ السَّمَوَاتِ السَّبْعِ وَرَبَّ الْعَرْشِ الْعَظِيْمِ كُنْ لِي جَارًا مِنْ فُلَانِ بْنِ فُلَانٍ، وَأَحْزَابِهِ مِنْ خَلَائِقِكَ (وَمِنْ شَرِّ خَلْقِكَ كُلِّهِمْ جَمِيْعًا) أَنْ يَفْرُطَ عَلَيَّ أَحَدٌ مِنْهُمْ أَوْ يَطْغَى عَزَّ جَارُكَ وَجَلَّ ثَنَاؤُكَ وَلَا إِلٰهَ إِلَّا أَنْتَ

Allaahumma Rabbas-samawaatis-sab'i, wa Rabbal-'Arshil-'Adheem, kun lee jaaran min [here you mention the person's name], wa 'ahzaabihi min khalaa'iqika, (wa min sharri khalqika kullihim jami'an) 'an yafruta 'alayya 'ahadun minhum 'aw yatghaa, 'azza jaaruka, wajalla thanaa'uka, wa laa 'ilaaha 'illaa 'Anta

O Allah, Lord of the seven heavens, Lord of the Magnificent Throne, be for me a support against [such and such a person] and his helpers from among your creatures, lest any of them abuse me or do me wrong. Mighty is Your patronage and glorious are Your praises. There is none worthy of worship but You. Narrated from Abdullah Ibn Masood (RA) and Abdullah Ibn Abbas (RA), they said: If anyone fears harm from any ruler, administrator or powerful person, he should recite this dua.

Reference: Sahih (Albani). Sahih Al-Targhib: 2237, Adabul Mufrad: 707