O Allaah forgive all my sins, the minute of them and the major of them

اللَّهُمَّ اغْفِرْ لِي ذَنْبِي كُلَّهُ دِقَّهُ وَجِلَّهُ أَوَّلَهُ وَآخِرَهُ سِرَّهُ وَعَلانِيَتَهُ

‘Allaahumma ighfirlee Dhanbee kullah, diqqahu wa jillahu, awwalahu wa aakhirahu, sirrahu wa alaaniyatahu

O Allaah forgive all my sins, the minute of them and the major of them, the first of them and the last of them, the ones committed secretly and openly.

[Collected by Muslim]

Taken from the Fatawaa of our Shaykh, Allaama,
The Mufti of the Kingdom of Saudi Arabia, Abdul Azeez bin Abdullaah Bin Baz

Translated by Abbas Abu Yahya
https://followingthesunnah.wordpress.com/2015/06/30/the-best-dua-supplication