paramount
of greater importance than anything else
integral
essential to completeness or functioning
instrumental
very important in causing something to happen
consequential
having significant effects
momentous
of great importance
pivotal
extremely important
seminal
influencial
salient
standing out
compulsory
required by law
requisite
required as a condition
indispensable
absolutely necessary
consummate
complete or perfect
unparalleled
having no equal in quality
quintessential
serving as the most perfect example
paradigm
a typical pattern of something
exemplify
to clearly show a quality
nominal
very small in amount
marginal
minor or limited
peripheral
outer in position or importance
tangential
not closely related to the main topic