all-important vs crucial

all-important and crucial both are adjectives.

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

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

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

all-important (adjective)	crucial (adjective)
of the greatest importance	of extreme importance; vital to the resolution of a crisis
	of the greatest importance
	having crucial relevance