Forgiveness for sins should be sought from Allah, for the most important thing a servant can ask his Lord for, is forgiveness for his sins or its inevitable consequence. Such as deliverance from Hell and entry into Paradise. The servant needs forgiveness from his Lord for his sins, because he makes mistakes every day and night and Allah alone can forgive all sins. The Messenger of Allah (ﷺ) said: My heart is invaded by unmindfulness, and I ask Allah's pardon a hundred times in the day.
Source: Sahih (Albani). Abu Dawud: 1515
Duas from IslamicAPI's Masnun Dua dataset (based on the Quran, hadith, Hisnul Muslim and Rahe Belayat). See the dataset