I think you can put them in chronological order, since it one determined what followed:
Japanese capture of Nanking aka Nanjing in 1937, which began Japan's Chinese campaign.
Russian defeat of Japan in Manchuria in 1939, which made Japan decide to attack the USA instead
The Battle of France in May-June 1940 which gave Hitler control of Western Europe
The sinking of the French fleet which finally convinced FDR that Churchill really meant to go on fighting.
The attack on Pearl Harbor that brought the USA into the war and gave Stalin the confidence to bring his Manchurian army westward and save Moscow at the eleventh hour.
The fall of Singapor whose psychological impact destroyed the British Empire
Stalingrad and the consequent German defeat at Kursk, from when on the Germans were in continual retreat.
British terror bombing because of the way it distracted Germany from concentration on the eastern front.
The battle of the Atlantic, which had Germany won it would have crippled the American campaign to liberate Europe..