This comment.

Since the OP only talks about racist hatred, I shall only consider the minorities targeted by the Nazi Regime on account of their ethnic status. I'm guessing that OP is using the number of people killed in the holocaust as their metric to rank ethnic groups in order of the hatred directed at them by the Nazis. While admittedly, the Jews and the Slavs were killed in the largest numbers, that doesn't deny the fact that you also have the Romani genocide. From the linked wikipedia article:

Under the rule of Adolf Hitler, a supplementary decree to the Nuremberg Laws was issued on 26 November 1935, defining Gypsies as "enemies of the race-based state", the same category as Jews. Thus, the fate of Roma in Europe in some ways paralleled that of the Jews.

Hence, you can't really say that the degree of hatred faced by the Romani was any less than that faced by the Jews or the Slavs, especially when they were arguably grouped in the same (or at least, similar) category. Furthermore, "most Blacks and persons of color" also fell under the category of Untermensch, and I doubt it's a good idea to imply that they somehow escaped Nazi hatred.

The Nazis believed that:

Mulattos and Finn-Asian barbarians, Gipsy’s and black skin savages all make up this modern underworld of subhuman’s that is always headed by the appearance of the eternal Jew.

Edit: Added a few more links, especially to the "Der Untermensch" text.