sincerity vs unassumingness

sincerity and unassumingness both are nouns.

Word	Noun	Adjective	Verb	Adverb
sincerity	Yes	No	No	No
unassumingness	Yes	No	No	No

As nouns, sincerity and unassumingness are synonyms defined as:

sincerity (noun)	unassumingness (noun)
the quality of being open and truthful; not deceitful or hypocritical	a quality of naturalness and simplicity
the trait of being serious
a quality of naturalness and simplicity
an earnest and sincere feeling