racist vs antiblack

racist is a noun but antiblack is not a noun.

Word	Noun	Adjective	Verb	Adverb
racist	Yes	Yes	No	No
antiblack	No	Yes	No	No

As adjectives, racist and antiblack are synonyms defined as:

racist and antiblack: discriminatory especially on the basis of race or religion

Other synonyms of racist include anti-Semite.

racist (noun)	antiblack (noun)
a person with a prejudiced belief that one racial group is superior to others

racist (adjective)	antiblack (adjective)
discriminatory especially on the basis of race or religion	discriminatory especially on the basis of race or religion
based on racial intolerance