が最後
(Ga saigo)
once X (happens), that's the end / if X, nothing can stop what follows.
Connection rules
- +V-た + が最後; V-たら + 最後.
- +Point of no return — once X, the consequence follows inevitably.
- +Literary / dramatic register.
Examples
1.
彼は寝たが最後、朝まで起きない。

Kare wa ne ta ga saigo, asa made oki nai.
Once he falls asleep, he won't wake until morning.
「once X (happens), that's the end / if X, nothing can stop what follows」
2.
言ってしまったら最後、もう戻れない。

I te shima tara saigo, mou modore nai.
Once you say it, there's no going back.
「once X (happens), that's the end / if X, nothing can stop what follows」
Practice
Once he grabs the microphone, he won't let go until the very end.
彼はマイクを___、最後まで放そうとしない。
Romaji also accepted