na-adjective
critical; in crisis
Describes a situation, state, or condition that is extremely serious or at a decisive turning point. Often used with nouns like 状況, 状態, or 段階.
会社は危機的な状況に陥っている。
The company is in a critical situation.
地球温暖化は危機的な段階に入った。
Global warming has entered a critical stage.
深刻 means 'serious' or 'grave', often for problems or expressions. 危機的 is stronger, implying an imminent crisis or turning point.
Compound of 危機 (kiki, 'crisis') and the adjectival suffix 的 (-teki, '-like, -ic'). The suffix 的 derives from Chinese 的 (de), used to form adjectives from nouns.