earth-shatteringly
I could only laugh at how earthshakingly terrible it all was.
Things that used to be earthshakingly important to her just didn't matter anymore.
People are given awards for doing things that are not always earthshakingly important.
These tips are not earthshakingly brilliant, but they may be helpful.
We are discussing issues that are earthshakingly important.

SMART Vocabulary: related words and phrases

Very important or urgent
all-important
at all costsidiom
be a matter of life and/or deathidiom
cardinally
chief
imperative
last but not leastidiom
leading
life-altering
life-and-death
life-changing
overriding
primary
prime
principally
prior
prized
seminal
tectonic
weighty

You can also find related words, phrases, and synonyms in the topics:

Surprising and shocking