https://en.wikipedia.org/wiki/Walter_Hallstein

In 1935, Hallstein attempted to start a military career alongside his academic duties.[17] In 1936, he managed to integrate a voluntary military service in an artillery unit.[17] In the years between 1936 and 1939, he attended several military courses[18] and was made a reserve officer.[17]

Hallstein was a member of several nominally Nazi professional organizations,[g][19] but he was not a member of the Nazi Party

Not the worst nazi but the voluntary military service under the Nazis seals the deal for me. Definitely a Nazi.