Obi Wan Kenobi

Empire far surpasses every other film in the saga and that's saying something considering how good the original and even Return of the Jedi were. While Star Wars had fantastic characters, the focus was more towards the adventure than exploring them (not to say it doesn't explore them, it does, just not with the depth of Empire). It's in Empire that they see the most struggle and development. Luke's training with Yoda and Han and Leia's romance are interminable. Then there's all the great battles, the Battle of Hoth, the asteroid chase, the duel and everything else on Bespin, but more important than all that is the characters. Without that, none of those things mean much.