retort vs come back

retort is a noun but come back is not a noun.

Word	Noun	Adjective	Verb	Adverb
retort	Yes	No	Yes	No
come back	No	No	Yes	No

As verbs, retort and come back are synonyms defined as:

Other synonyms of retort include rejoin, repay, return, riposte.

retort (noun)	come back (noun)
a vessel where substances are distilled or decomposed by heat
a quick reply to a question or remark (especially a witty or critical one)