superlative vs acme

superlative and acme both are nouns.

Word	Noun	Adjective	Verb	Adverb
superlative	Yes	Yes	No	No
acme	Yes	No	No	No

As nouns, superlative and acme are synonyms defined as:

superlative and acme: the highest level or degree attainable; the highest stage of development

Other synonyms of superlative include elevation, height, meridian, peak, pinnacle, summit, tiptop, top.

superlative (noun)	acme (noun)
an exaggerated expression (usually of praise)	the highest point (of something)
the superlative form of an adjective or adverb	the highest level or degree attainable; the highest stage of development
the highest level or degree attainable; the highest stage of development

superlative (adjective)	acme (adjective)
highest in quality