Man, hunting for those specific Percy-gets-justice fics is a whole mood. I've noticed the quality varies wildly by platform, not just by author. AO3 is the undisputed champion for this trope, hands down. The tagging system lets you filter for 'Aftermath of Child Abuse' or 'Whump' alongside 'Percy Jackson & the Olympians', which instantly weeds out the fics where the reveal is just a cheap drama beat. You'll find sprawling, multi-chapter epics that really sit with the psychological fallout, like 'fracture lines' or 'the weight of a name'.
Tumblr still has some amazing, tightly-written one-shots buried in the tags, but you have to dig through a mountain of headcanon posts and moodboards. The good ones hit like a truck because they're so focused on a single, visceral moment of realization from another character's POV. FF.net is a wasteland for this, honestly—too many poorly-tagged 'betrayal' fics that miss the point entirely. If you're after that specific catharsis of the camp or the gods finding out, AO3's curation power is unmatched. The comment sections there also tend to be more thoughtful, which really adds to the experience of reading something that heavy.