The Moments That Made Fans Cry
The ones everyone names
Dobby's death and Fred's death top most lists, and for different reasons. Dobby is a character who starts as comic relief and ends as someone willing to die for his friends. His final words, spoken with simple dignity, land because the reader has watched his entire arc across four books.
Fred's death is devastating because it's sudden, barely described, and happens to the character who represents joy. The Weasley twins are the comic engine of the series, and losing one of them feels like the story losing its sense of humour.
Dumbledore's death is the structural shock. It changes what the story is, not just what happens in it. From that point forward, Harry is alone, and the safety net the reader has relied on for six books is gone.
The ones that sneak up on you
The Mirror of Erised scene in book one is quiet and easily missed on a first read. Harry finds a mirror that shows the deepest desire of whoever looks into it, and he sees his dead parents standing around him. He goes back night after night, just to look at them. Dumbledore gently tells him to stop.
The moment that destroys most readers on a reread is Snape's memories in the final book. Knowing the end changes everything about how you read his scenes. Every cruel remark, every suspicious glance, every apparent betrayal looks different when you know what he was actually doing and why.
Neville visiting his parents in St Mungo's is a single scene in book five, and it might be the saddest in the series. His parents were tortured into insanity and don't recognise him. His mother gives him a sweet wrapper, and he keeps it, even though everyone tells him to throw it away. He keeps every one.