second banana vs foot soldier

second banana and foot soldier both are nouns.

Word	Noun	Adjective	Verb	Adverb
second banana	Yes	No	No	No
foot soldier	Yes	No	No	No

As nouns, foot soldier is a hypernym of second banana; that is, foot soldier is a word with a broader meaning than second banana:

second banana: someone who serves in a subordinate capacity or plays a secondary role
foot soldier: an assistant subject to the authority or control of another

Other hypernyms of second banana include subordinate, subsidiary, underling.

second banana (noun)	foot soldier (noun)
a performer who acts as stooge to a comedian	fights on foot with small arms
someone who serves in a subordinate capacity or plays a secondary role	an assistant subject to the authority or control of another