Complex sentence: "Retro" has highly conrtoversial in that it was a concept album describing the demise of a relationship because of infidelity, in fact, many argue it describes the demise of Urban's relationship with his wife at the time.
Split into simpler sentences: Retro has highly controversial in that it was a concept album describing the demise of a relationship because of infidelity. In fact, many argue it describes the demise of Urban's relationship with his wife at the time.