What finally ended the Great Depres-
sion (three words)

World War II.

Explanation:

By pursuing economic reforms to solve the financial crisis, Roosevelt introduced an economic reform package called the New Deal. These reforms partially addressed the problems of the economic crisis. However, this set of economic reforms has not thoroughly solved the accumulated problems. The crisis ceased at the beginning of the Second World War because, in this way, absolutely every segment of life changed. So the end of the economic crisis began at the beginning of World War II.