Sviatoslav Richter "Chopin Etude" (the fastest on record btw)
However, Richter was Horowitz's only REAL competition at the time. To Horowitz's advantage, Richter wasn't allowed out of the Soviet Union for fear that he might defect. Horowitz had long since defected before the war and was raising money for troops with an arrangement of Stars and Stripes that would bring the house down.
Horowitz respected Richter and Richter was the only pianist that Horowitz would admit was good, but Richter had a mighty big dollop of jealousy for Horowitz and said that Horowitz played like a Clown.
There rivalry was well known and there were 'camps' who claimed the other was better.