knockout punch vs KO punch

knockout punch and KO punch both are nouns.

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

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

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

Other synonyms of knockout punch include haymaker, Sunday punch.

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