The comic book character Superman was created in 1933 by two Jewish guys who presumably were not Nazis.
The term superman is -- or was, for a while -- generally translated into German as Uebermensch. The Nazis often referred to themselves as Uebermenschen. The German term Uebermensch was coined by Nietzsche, who hated anti-Semites and racists in general.
In English, before the creation of the comic book character, the most prominent user of the term superman was George Bernard Shaw, also an anti-racist. Some people think that Shaw's support of eugenics was racist, but, on the contrary, he favored breeding across ethnic and class lines -- the exact opposite of racist goals of "racial purity." In direct opposition to racist pseudo-science, Shaw's assertions that benefits would come from broadening the gene pool are scientifically sound.
Nietzsche first mentions the Uebermensch in Also sprach Zarathustra, published in 1883. Shaw first mentioned the superman in his play Man and Superman, written in 1903, first performed in 1905. It has often been erroneously asserted that Shaw got many of his ideas directly from from Nietzsche. Shaw himself attempted to clear this up, saying that, although he liked Nietzsche's works very much, he first began to read them after he had read assertions that he had gotten various ideas from Nietzsche -- but the error persists. When Shaw read Nietzsche, he found that they had much in common -- such as being frequently misunderstood by people who very annoyingly claimed to be championing their causes without first having gone to the trouble of reading their works.
An annoying tendency which still hasn't died out.