What is the meaning of the noble Hadith: "Whoever seeks out the faults of people," and does viewing forums and pornographic images fall under seeking out faults? And what are the consequences for one who sent private pictures to young men and fears their spread or their remembrance of them, and is there repentance and forgiveness for that?

The aforementioned Hadith prohibits harming Muslims, shaming them, and seeking out their private matters. For whoever seeks out the private matters of his Muslim brother, Allah will seek out his private matters and expose him. This does not include one who openly commits sins.

Looking at nude pictures is not among the seeking out of private matters prohibited in the Hadith, but it is forbidden from the perspective of unleashing one's gaze upon what Allah has prohibited. Allah has commanded believing men and believing women to lower their gaze.

Sincere repentance for these sins is obligatory, involving remorse, cessation, and not returning to them. Allah accepts sincere repentance, no matter how great the sins. Your pictures being with others will not harm you after your repentance, for Allah does not burden a soul beyond its capacity.