dressed-up vs dressed to kill

dressed-up and dressed to kill both are adjectives.

Word	Noun	Adjective	Verb	Adverb
dressed-up	No	Yes	No	No
dressed to kill	No	Yes	No	No

As adjectives, dressed-up and dressed to kill are synonyms defined as:

Other synonyms of dressed-up include dolled up, dressed, dressed to the nines, spiffed up, spruced up, togged up.

dressed-up (adjective)	dressed to kill (adjective)
dressed in fancy or formal clothing	dressed in fancy or formal clothing