big enchilada vs big shot

big enchilada and big shot both are nouns.

Word	Noun	Adjective	Verb	Adverb
big enchilada	Yes	No	No	No
big shot	Yes	No	No	No

As nouns, big enchilada and big shot are synonyms defined as:

Other synonyms of big enchilada include big cheese, big deal, big fish, big gun, big wheel, head honcho.

big enchilada (noun)	big shot (noun)
an important influential person	an important influential person