It would have been so much better if “Harry Potter and the Deathly Hallows - Part 2” movie would have sticked to the books at least for the Battle of Hogwarts. Right from the point when Professor Minerva McGonagall summons the men in armour to protect Hogwarts and Mrs. Weasly gives a confused look to the ending when Harry and Voldermort were dueling in some other corner of Hogwarts away from the battle.
I may not have a deep understanding of movie making, but it would have been more exciting to see Harry who is presumed dead to appear out of nowhere while shielding Mrs. Weasely from Voldermort and initiating the duel. I feel the makers of the movie thought that they should associate more importance to Harry Potter by showing him alive right at the beginning of the stand off between the Death Eaters led by Lord Voldermort and Order of the Phoenix led by Neville Longbottom at that point.
It is the importance that you give to the other minor characters that makes a book or movie well defined. While Neville Longbottom opposed Lord Voldermort at the stand off in the movies, they showed the fight to initiate when Harry jumped off from Hagrid’s arms. In the books however it starts when Neville chops off the head of Nagini, the last horcrux of Lord Voldermort. In the books Harry Potter hides under the invisibility cloak during the battle protecting the members of the Order of the Phoenix now and then. But in the movies Harry and Lord Voldermort keep dueling at some other corners of the school.
Also, in the books it was beautifully narrated how Mrs. Weasely came in between Bellatrix and Genie when the former attacked her. The fight was gripping to the point Mrs. Weasely kills Bellatrix. And that is when Lord Voldermort attacks Mrs. Weasely and Harry comes in between to rescue her. It also showed that Lord Voldermort may have had a soft corner for Bellatrix. Also, at this point of time Harry and Lord Voldermort are in the middle of the duel with both sides watching. This is when Harry explains Lord Voldermort why he could never use the Elder Wand to harm him. This is the point when most readers who had lost some confidence on Harry’s intelligence (though not on his courage) feel that well the boy is something and had been observant. This was a theory that had even Hermione had missed but was registered by Harry. It showed the brilliance of the protagonist.
On the other hand in the movies, Neville kills Nagini after gaining consciousness from Lord Voldermort’s attack. This he does while trying to save Ron and Hermione. Mrs. Weasely kills Bellatrix in a totally different part of the battle. Harry and Lord Voldermort are fighting at some open space outside Hogwarts with nobody around. This is supposed to be the most epic duel of the entire Harry Potter series and it is seemed to have been handled with a disinterest. Not that other wizards from both sides watching the duel would make any difference, but it would have showcased the magnanimity of this fight. Finally, after the battle while Harry, Ron and Hermione were taking a stroll, he explains why Lord Voldermort could not hurt him using the Elder Wand as it belonged to Harry.
Plot changes are common when it comes to translating a book into a movie, but those are meant to make the movies more interesting. Even for a person who has not read the books, I reckon that the ending showcased at the conclusion of the book would have been much more interesting than the one in the movie.