What European country did japan defeat in the twentieth century?

None, actually. They defeated Russia in the Russo-Japanese War (1904-1905) and expelled them from Manchuria, which they had occupied in 1903.

They also occupied parts of China, the Phillipines, Indochina, and New Guinea during the 2nd Sino-Japanese War (1937-1945) and World War II (1939-1945)