once
now that
as soon as
Structure
- verb[た] + が + 最後
- Verb[たら] + 最後
[Aが最後B and Aたら最後B are used to emphasize that once situation A happens or now that situation A has happened, “it is over” and situation B arises which nothing can be done]
[Often expresses the speaker’s negative evaluation. Sometimes sentence B is omitted]
[Expressions like 一旦、一度 are common in phrase A, and でも、もう、2度と、どうしても、絶対に、てしまう and verbs in negative potential forms are common in phrase B]