Franklin Rosevelt -supervised the mobilization of the U.S. economy to support the war effort, and implemented a Europe first strategy, making the defeat of Germany a priority over that of Japan.
Winston Churchill- rallied the British people and led the country from the brink of defeat to victory. He shaped Allied strategy in the war, and in the war's later stages he alerted the West to the expansionist threat of the Soviet Union.
Neville Chamberlin- served as British prime minister from 1937 to 1940 and is best known for his policy of "appeasement" toward Adolf Hitler's Germany. He signed the Munich Agreement in 1938, relinquishing a region of Czechoslovakia to the Nazis. In 1939, Britain declared war on Germany.
(I will put the others in the comments)