Uncle Tom vs Negro

Uncle Tom and Negro both are nouns.

Word	Noun	Adjective	Verb	Adverb
Uncle Tom	Yes	No	No	No
Negro	Yes	No	No	No

As nouns, Negro is a hypernym of Uncle Tom; that is, Negro is a word with a broader meaning than Uncle Tom:

Uncle Tom: (ethnic slur) offensive and derogatory name for a Black man who is abjectly servile and deferential to Whites
Negro: a person with African ancestry, "Negro" and "Negroid" are archaic and pejorative today

Other hypernyms of Uncle Tom include African-American, Black, Negroid, Black person, blackamoor.

Uncle Tom (noun)	Negro (noun)
a servile black character in a novel by Harriet Beecher Stowe	a person with African ancestry, "Negro" and "Negroid" are archaic and pejorative today
a servile black character in a novel by Harriet Beecher Stowe
(ethnic slur) offensive and derogatory name for a Black man who is abjectly servile and deferential to Whites