Not gonna lie, if you're looking for fics that really dig into the heart of Midoriya Izuku's pain, 'Yesterday Upon The Stair' is pretty much the definitive piece for me. It's a ghost quirk AU where Izuku can see spirits, and the isolation and quiet agony of that ability is just palpable. The author doesn't just rehash canon sad moments; they build this whole internal world of grief and longing around him. It's less about dramatic crying and more about the weight of being seen yet completely alone, of holding conversations no one else can hear. That kind of melancholy lingers in every chapter.
Another one that messed me up good is 'Breathe In, Breathe Out' by LandofMistAndSecrets. It deals with his anxiety and panic attacks post-All Might training, but in such a granular, physical way. You feel the tightness in his chest, the way his thoughts spiral during a villain attack. It's not romanticized suffering—it's exhausting and raw, and sometimes the saddest part is watching him put on a brave face for his friends afterward. The emotional payoff isn't a big victory, but small moments of understanding that feel earned.
Honestly, a lot of hurt/comfort fics miss the mark by making the 'comfort' too quick or easy. The best ones let the sadness sit, let Izuku be wrong or broken for a while without rushing to fix him. Those stories often hit harder because they respect the complexity of his character beyond just being a crybaby. He's resilient, but that resilience is born from a deep well of past hurt, and fics that tap into that source material, both canon and original, leave the biggest impression.