My favorite part has to be the scene at the end when the Golden Trio is holding hands and standing in front of the ruins. It unites the first book to the seventh book. To me it says that in all of the previous books, everyone fights over petty things because they do not know what they can lose: friends, family, that beautiful Hogwarts castle. In the end, when the castle is in ruins, it really hits everyone that they need to stay united no matter who they are by blood, but what is important is the things they believe in: equality, friendship, love, etc. As Remus Lupin said, "It's the quality of one's convictions that determines success, not the number of followers."