Our most beloved Prophet Muhammad (SAW) offered supplication (du'a) at times of calamity on a number of occasions in the time of extreme distress and need thus beseeching Allah (SWT) for His Mercy and benevolence. Rasulullah (SAW) read Qunut Nazilah for the salvation of the weak and oppressed in Makkah.

This Qunut was also read by Rasulullah (SAW) when the incident massacre of the 60 al hafiz companions for a month based on the following hadith:

Meaning: The Prophet sallallahu `alaihiwasallam have read qunut prayer not only at dawn when they massacre his al hafiz companions.
-Bukhari and Muslim-

HOW TO RECITE QUNUT NAZILAH

Qunut Nazilah can be recited at all obligatory prayers: Zuhur, Asar, Maghrib, Isya’ and Subuh. It can be recited at the final rak’at after getting up from Ruku’ for I’tidal.

The prayer is recited while standing for I’tidal. There are three ways to recite the prayer. The imam may select any of the followings:

Recite the Qunut as normally recited during Subuh prayer.
Recite the Qunut Nazilah only as per attached.
Recite the Subuh Qunut followed by Qunut Nazilah.

Reminder:

If the Imam does not memorise the Qunut Nazilah attached, recite the Qunut as normally recited in Subuh prayer. Then, Qunut Nazilah can be recited after the prayer.
The Imam needs to inform the followers that Qunut will be recited in the prayer so that they can “ameen” the prayer.

QUNUT NAZILAH

Which means:

“'O Allah, we seek Your help; we beseech Your forgiveness; we seek guidance from You; we affirm our faith in You; we bow to Thee and we praise You; we are grateful and do not infidel; we reject and abandon everyone who forsakes You.

‘O Allah, You alone do we worship; unto You alone we pray; and before You alone we prostrate in worship; unto You alone we strive and implore;we cherish hope in Your mercy; we fear Your chastisement; most certainly, Your stern punishment will overtake those who reject the truth.

‘O Allah, may honour be with Islam and Muslims. Stop all kinds of tyranny and hostility. Help our oppressed brethren wherever they are. Lift them from their hardships, plagues, war and hostility. O Allah, save us from all evil and do not make our place the place of calamity; avert us from any disaster because only You can avert it, O Allah.”

Source and credits:
http://www.islam.gov.my/en/guide-qunut-nazilah