decisive
adj.adj. able to make decisions quickly and with confidence. It also describes an action or event that settles a situation or leads to a final result.
adj. characterised by the ability to make choices firmly and without hesitation; also used to describe an event or factor that determines a final outcome or settles a dispute.
She is a very decisive leader who acts quickly.
The manager's decisive action during the crisis prevented the company from losing its most important clients.
The battle proved to be the decisive moment of the war, shifting the balance of power and forcing the opposing side to negotiate for peace.
From Middle French décisif, equivalent to decide + -ive.
Often used to describe personality traits or the conclusive nature of an event.