Dua for forgiveness, Sayyid al-Istighfar.

اللَّهُمَّ أَنْتَ رَبِّي لَا إِلَهَ إِلَّا أَنْتَ، خَلَقْتَنِي وَأَنَا عَبْدُكَ، وَأَنَا عَلَى عَهْدِكَ وَوَعْدِكَ مَا اسْتَطَعْتُ، أَعُوذُ بِكَ مِنْ شَرِّ مَا صَنَعْتُ، أَبُوءُ لَكَ بِنِعْمَتِكَ عَلَيَّ، وَأَبُوءُ لَكَ بِذَنْبِي، فَاغْفِرْ لِي، فَإِنَّهُ لَا يَغْفِرُ الذُّنُوبَ إِلَّا أَنْتَ

Allāhumma anta rabbī lā ilāha illā ant, khalaqtanī wa ana ʿabduk, wa ana ʿalā ʿahdika wa waʿdika mastaṭaʿt, aʿūdhu bika min sharri mā ṣanaʿt, abūʾu laka bi-niʿmatika ʿalayya, wa abūʾu laka bi-dhambī, faghfir lī, fa-innahū lā yaghfirudh-dhunūba illā ant

O Allah, You are my Lord, there is no god but You. You created me and I am Your servant, and I keep Your covenant and promise as best I can. I seek refuge in You from the evil of what I have done. I acknowledge Your favour on me and I acknowledge my sin, so forgive me, for none forgives sins but You.

قَالَا رَبَّنَا ظَلَمْنَآ أَنفُسَنَا وَإِن لَّمْ تَغْفِرْ لَنَا وَتَرْحَمْنَا لَنَكُونَنَّ مِنَ ٱلْخَٰسِرِينَ

Rabbanā ẓalamnā anfusanā wa illam taghfir lanā wa tarḥamnā lanakūnanna minal-khāsirīn

Our Lord, we have wronged ourselves, and if You do not forgive us and have mercy on us, we will surely be among the losers. (The dua of Adam and Hawwa)

أَسْتَغْفِرُ اللَّهَ وَأَتُوبُ إِلَيْهِ

Astaghfirullāha wa atūbu ilayh

I seek Allah's forgiveness and turn to Him in repentance.