consequential
adj.important or having a significant effect on the future. You use this to describe a decision or event that will change things in a big way.
adj.having significant or far-reaching consequences; important. Often describes events, decisions, or historical periods that alter the course of future developments.
“The court's decision was highly consequential for the whole country.”
“The discovery of the new vaccine proved to be the most consequential event of the decade for global health.”
“Historians argue that the 1914 assassination was the most consequential act of the century, as it triggered a series of alliances that led directly to global conflict.”
Often modified by degree adverbs like 'highly', 'deeply', or 'immensely'.
“For online platforms, the period immediately following legal reform appears particularly consequential, as communities recalibrate and some voices push back.”
“In the longer term, the order’s most consequential provisions are aimed at state school vaccination requirements, which is where American vaccine policy is actually made.”
From consequent + -ial.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.