Anti-nazi

a member of the National Socialist German Workers’ Party, which controlled Germany from 1933 to 1945 under Adolf Hitler and advocated totalitarian government, territorial expansion, anti-Semitism, and Aryan supremacy, all these leading directly to World War II and the Holocaust.
(often lowercase) a person elsewhere who holds similar views.
(often lowercase) Sometimes Offensive. a person who is fanatically dedicated to or seeks to regulate a specified activity, practice, etc.:
a jazz nazi who disdains other forms of music; health nazis trying to ban junk food.
of or relating to the Nazis.
Contemporary Examples

Flash forward to our own bloody 20th century and the Nazi bonfires of Jewish, anti-nazi, and other “degenerate” books.
History’s Greatest Book Burners Judith Miller September 6, 2010

And worth remembering that from the moment the war began, Hollywood was on message with anti-nazi propaganda.
Did Hollywood Collaborate With Hitler? A New Book Makes Bold Claims. Christopher Bray September 8, 2013

The film contained strong anti-war themes and was perceived by Nazi officials to have anti-nazi messages.
Speed Read: The Craziest Bits From ‘How Hitler Helped Hollywood’ Victoria Kezra July 30, 2013

The only other anti-nazi caricatures to appear during the Third Reich were those that were published abroad.
When Hitler Was a Punchline Rudolph Herzog May 13, 2011

adjective
opposing any individual or group that espouses Nazi ideologies
noun
a person who is opposed to Nazism
noun (pl) Nazis
a member of the fascist National Socialist German Workers’ Party, which was founded in 1919 and seized political control in Germany in 1933 under Adolf Hitler
(derogatory) anyone who thinks or acts like a Nazi, esp showing racism, brutality, etc
adjective
of, characteristic of, or relating to the Nazis

1930, noun and adjective, from German Nazi, abbreviation of German pronunciation of Nationalsozialist (based on earlier German sozi, popular abbreviation of “socialist”), from Nationalsozialistische Deutsche Arbeiterpartei “National Socialist German Workers’ Party,” led by Hitler from 1920.

The 24th edition of Etymologisches Wörterbuch der deutschen Sprache (2002) says the word Nazi was favored in southern Germany (supposedly from c.1924) among opponents of National Socialism because the nickname Nazi, Naczi (from the masc. proper name Ignatz, German form of Ignatius) was used colloquially to mean “a foolish person, clumsy or awkward person.” Ignatz was a popular name in Catholic Austria, and according to one source in World War I Nazi was a generic name in the German Empire for the soldiers of Austria-Hungary.

An older use of Nazi for national-sozial is attested in German from 1903, but EWdS does not think it contributed to the word as applied to Hitler and his followers. The NSDAP for a time attempted to adopt the Nazi designation as what the Germans call a “despite-word,” but they gave this up, and the NSDAP is said to have generally avoided the term. Before 1930, party members had been called in English National Socialists, which dates from 1923. The use of Nazi Germany, Nazi regime, etc., was popularized by German exiles abroad. From them, it spread into other languages, and eventually was brought back to Germany, after the war. In the USSR, the terms national socialist and Nazi were said to have been forbidden after 1932, presumably to avoid any taint to the good word socialist. Soviet literature refers to fascists.
German Nationalsozialistische [deutsche Arbeiter-Partei] (National Socialist [German Workers’ Party])