The primary contribution Adolf Hitler made to German society was that he totally destroyed Germany: in 1945, Germany was literally in ruins. Millions upon millions of people were dead. Millions more were homeless and starving (in Germany, not just in the countries Germany invaded). Germany had no economic, no coherent political system, no communications system, no libraries, no schools, no hospitals. In a sense German society did not exist in 1945 and had to be rebuilt from scratch to become modern Germany.

One might mention things that Hitler did ostensibly to benefit Germans before 1939, but faced with the legacy of the National Socialist dictatorship and what state Germany was in in 1945, such things are laughable at best as "contributions to society."