Warner Bros.
The bloody battle saw Voldemort's forces descend on Harry Potter, his teachers, his classmates, and the secret society of wizards against Voldemort, The Order of the Phoenix.
This year, Rowling chose to explain why Remus Lupin "had to die."
Professor Lupin was a friend of Harry Potter's parents while they attended Hogwarts, and became one of Harry's substitute parents. He was also a werewolf, having been bitten by the werewolf Greyback at a young age. He died during the Battle of Hogwarts. His death hit fans especially hard, because his wife Tonks also died, leaving their young son an orphan.
Once again, it's the anniversary of the Battle of Hogwarts so, as promised, I shall apologise for a death. This year: Remus Lupin.
- J.K. Rowling (@jk_rowling) May 2, 2016
In the interests of total honesty I'd also like to confess that I didn't decide to kill Lupin until I wrote Order if the Phoenix.
- J.K. Rowling (@jk_rowling) May 2, 2016
Arthur lived, so Lupin had to die. I'm sorry. I didn't enjoy doing it. The only time my editor ever saw me cry was over the fate of Teddy. ??
- J.K. Rowling (@jk_rowling) May 2, 2016
Last year, on this day, Rowling apologized for killing Fred Weasley during the Battle, which she said was the "worst [death] for me, so I started with him."