all important vs all-important

all important and all-important both are adjectives.

Word	Noun	Adjective	Verb	Adverb
all important	No	Yes	No	No
all-important	No	Yes	No	No

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

Other synonyms of all important include crucial, essential, of the essence.

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