Richard Sorge was a Russian spy in Imperial Japan during WWII, and was arguably the most valuable spy throughout the war. There are even rumors that he fairly accurately predicted the date of Operation Barbarossa to Stalin, but Stalin didn't pay him any heed.
WI Sorge would have been listed to by Stalin more? Granted, his information was invaluable to the Soviets in the first place. But what if some of the information he passed on that turned out to be extremely valuable (with historical hindsight) was listened to? Could the USSR have come out of WWII in a better position, or maybe even survived Barbarossa better?