I want to say Rem but you are right about Subaru. His character development throughout the story is amazing and i love to see characters struggle so hard as he did. I really wanted Rem to get together with Subaru. What did you think of the ending ? I mean some people would get disappointed because throughout the anime they make us think that the story will continue but then it never does. Like how they show "Felt" taking part but is not even essential to the story or effect it as much. But i have only seen the anime so might be different in the manga.