Sunday punch vs knockout punch

Sunday punch and knockout punch both are nouns.

Word	Noun	Adjective	Verb	Adverb
Sunday punch	Yes	No	No	No
knockout punch	Yes	No	No	No

As nouns, Sunday punch and knockout punch are synonyms defined as:

Sunday punch and knockout punch: a hard punch that renders the opponent unable to continue boxing

Other synonyms of Sunday punch include haymaker, KO punch.

Sunday punch (noun)	knockout punch (noun)
a hard punch that renders the opponent unable to continue boxing	a hard punch that renders the opponent unable to continue boxing