I have to say that my fav. underrated couples is MyungGyu. During YAMO L was almost always Gyu's backup. L really looks up to Gyu. The best part of Seame player was when Gyu and L got left home alone. They really are the two members that are the most comfortable with eachother.
I think a lot of their relationship stems from the fact that when Infinite was first formed L was the baby of the group. Guy and Dongwoo both take care of L.