sure thing vs foregone conclusion

sure thing and foregone conclusion both are nouns.

Word	Noun	Adjective	Verb	Adverb
sure thing	Yes	No	No	No
foregone conclusion	Yes	No	No	No

As nouns, sure thing and foregone conclusion are synonyms defined as:

Other synonyms of sure thing include certainty.

sure thing (noun)	foregone conclusion (noun)
something that is certain	something that is certain
	an inevitable ending