What is the big turning point of World War 2 in Europe?

The major turning point in the Western Front occurred in two places in the same week. In Italy, Rome surrendered and the Italian Army was taken out of the war, June 4, 1944. In France, the D-Day invasion began on June 6, 1944, completing a cross-channel invasion that Hitler said could not be done.

The major turning point in the East could be considered Stalingrad in the winter of 1942-43, or Kursk in the summer of 1943. After the huge German offensive toward Kursk failed, the German Army was never again capable of a major attack against the Soviets. The Eastern Front absorbed hundreds of thousands of German casualties in 1943.