spruced up vs dressed to kill

spruced up and dressed to kill both are adjectives.

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

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

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

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