critical moment; crucial point; crossroads
Refers to a decisive juncture or turning point where an important outcome is determined. Often used in formal or written contexts.
The negotiations have reached a critical juncture.
I was brought to a crossroads in my life.
The exact derivation is uncertain; the kanji 関 (barrier, connection) and 頭 (head, top) together suggest a pivotal point or barrier to be overcome.