fine-tooth comb vs scrutiny

fine-tooth comb and scrutiny both are nouns.

Word	Noun	Adjective	Verb	Adverb
fine-tooth comb	Yes	No	No	No
scrutiny	Yes	No	No	No

As nouns, scrutiny is a hypernym of fine-tooth comb; that is, scrutiny is a word with a broader meaning than fine-tooth comb:

Other hypernyms of fine-tooth comb include examination.

fine-tooth comb (noun)	scrutiny (noun)
a method of examining in minute detail	the act of examining something closely (as for mistakes)
a comb with teeth set close together	a prolonged intense look