80s Trivia: Which of these boxers does Rocky never defeat in a sanctioned match?

You can't think 80s movies without thinking of Rocky. Spanning six movies in four decades, the Rocky series is widely regarded as one of the best ever, featuring a story that likely all of us can relate to  in some way.  Rocky was known for his boxing prowess and his incredible fighting record, eventually beating almost all fighters that stood with him in the ring.  Not all of them, however.

Off of Pocket Trivia: 80s Trivia:  Which of these fighters did Rocky never beat in a sanctioned match?  Clubber Lang, Tommy Gunn, Ivan Drago or Apollo Creed?