Sunni Islam vs religious sect

Sunni Islam and religious sect both are nouns.

Word	Noun	Adjective	Verb	Adverb
Sunni Islam	Yes	No	No	No
religious sect	Yes	No	No	No

As nouns, religious sect is a hypernym of Sunni Islam; that is, religious sect is a word with a broader meaning than Sunni Islam:

Other hypernyms of Sunni Islam include religious order, sect.

Sunni Islam (noun)	religious sect (noun)
one of the two main branches of orthodox Islam	a subdivision of a larger religious group