Honestly, the Archive of Our Own tag system is unmatched for this. If you filter by the Bakugou Katsuki/Midoriya Izuku tag and then sort by kudos or bookmarks, you'll hit the heavy hitters. But the real trick is using additional filters. Try adding tags like 'Angst', 'Emotional Hurt/Comfort', or 'Psychological Trauma'. That weeds out the fluffier stuff fast.
I'd also recommend looking for authors who write a lot for other intense pairings or serious themes. Someone who does great Shigaraki backstory fics often brings that same depth to bakudeku. My last great find was a story that used their shared history of childhood bullying not just as a backdrop, but to explore how they both internalized violence in totally different ways. It wasn't a comfortable read, but it felt painfully real.
Sometimes the summaries give it away, too. Vague, poetic summaries often signal a more literary approach.