This is the 3168th most frequent Korean word.
결정적인
Decisive.
Here, "결정적인" describes a moment as being pivotal or decisive.
그 결정적인 순간이 우리의 승리를 이끌었다.
That crucial moment led to our victory.
In this sentence, "결정적인" qualifies evidence as being critical or conclusive.
결정적인 증거가 없어서 그는 무죄로 판정되었습니다.
He was found not guilty due to lack of decisive evidence.
"결정적인" in this context characterizes the moment as imperative and requiring resolution.