Here is a dua for forgiveness from the Quran:

Arabic: رَبَّنَا إِنَّنَا آمَنَّا فَاغْفِرْ لَنَا ذُنُوبَنَا وَقِنَا عَذَابَ النَّارِ

Transliteration: Rabbana innanā āmannā faghfir lanā dhunūbanā wa qinā 'adhāba al-nār.

Translation: "Our Lord, indeed we have believed, so forgive us our sins and protect us from the punishment of the Fire."

This dua is from Surah Al-'Imran (3:16), and it's a prayer for forgiveness and protection from the punishment of Hellfire. It encapsulates a believer's plea for mercy and forgiveness from Allah after acknowledging faith.