dressed vs dressed to kill

dressed and dressed to kill both are adjectives.

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

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

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

dressed (adjective)	dressed to kill (adjective)
dressed or clothed especially in fine attire; often used in combination	dressed in fancy or formal clothing
(of lumber or stone) to trim and smooth
treated with medications and protective covering
dressed in fancy or formal clothing