all-important vs of the essence

all-important and of the essence both are adjectives.

Word	Noun	Adjective	Verb	Adverb
all-important	No	Yes	No	No
of the essence	No	Yes	No	No

As adjectives, all-important and of the essence are synonyms defined as:

Other synonyms of all-important include all important, crucial, essential.

all-important (adjective)	of the essence (adjective)
of the greatest importance	of the greatest importance