buster vs small fry

buster and small fry both are nouns.

Word	Noun	Adjective	Verb	Adverb
buster	Yes	No	No	No
small fry	Yes	No	No	No

As nouns, small fry is a hypernym of buster; that is, small fry is a word with a broader meaning than buster:

Other hypernyms of buster include child, fry, kid, minor, nestling, nipper, shaver, tiddler, tike, tyke, youngster.

buster (noun)	small fry (noun)
a person (or thing) that breaks up or overpowers something	someone who is small and insignificant
a person who breaks horses	a young person of either sex
a robust child
an informal form of address for a man
a person born in the generation following the baby boom when the birth rate fell dramatically