1
general::
Phrase(s): return the compliment [and] return someone’s compliment
to pay a compliment to someone who has paid you a compliment. • Mary told me that my hair looked nice, so I returned her compliment and told her that her hair was lovely. • When someone says something nice, it is polite to return the compliment.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Also, return the favor. Repay someone in kind, as in Her political opponent came out with a smear campaign, and she returned the compliment. Neither the compliment nor the favor in this idiom is necessarily desirable. [First half of 1700s]
American Heritage Idioms