pivotal
adj.adj. extremely important because other things depend on it. You use this to describe a moment, person, or decision that changes the direction of a story or plan.
adj. of crucial importance in relation to the development or success of something else. Often used to describe a turning point or a central figure in a narrative or process.
The goal was a pivotal moment in the match.
The manager's decision to invest in new technology proved pivotal for the company's long-term survival.
Historians often debate which specific battle was the most pivotal, as a single shift in strategy could have altered the entire trajectory of the war.
From pivot + -al.
Often follows a linking verb like 'be' or 'prove', or precedes nouns like 'role', 'moment', or 'figure'.