Better words
Words you can use instead of important

Important is a very general word. Here are some words with more specific meanings that sound more natural and appropriate in particular situations.

people
influential, leading, of importance, of consequence, prominent, senior, top

events
key, historic, landmark, major, main, momentous

issues/problems
critical, major, of significance, significant
achievements/ discoveries
groundbreaking, historic, landmark, of consequence, of significance, significant

effects
far- reaching, lasting, main, major, significant

facts
notable, noteworthy, of importance, of note, significant

things that are important because you must have or do them
central, critical, crucial, essential, a matter of life and death, necessary, paramount, urgent, vital