Who was the first player to beat both Karpov and Kasparov in the same tournament ?

Vassily Ivanchuk achieved the rare feat of defeating both Anatoly Karpov and Garry Kasparov in the same tournament (Linares 1991). This was particularly remarkable because Karpov and Kasparov dominated world chess for nearly two decades. Anand, Kramnik, and Topalov were great players but this specific distinction belongs to Ivanchuk.