This one is so easy to answer and I am guessing not many people will go for this relationship. But my favorite in the whole series is Tonks and Lupin. It’s not really highlighted in the films, and hardly gets so much of a mention. But in the book it really blew me away, how she started changing because he rejected her. He did not want to harm her with being a werewolf and thought she was best well away from him. But they do get together and married in the end. Also contributed to sobbing whilst reading the Deathly Hallows.