No, I understand the second meaning well. In it, as you say, しまう adds a nuance beyond its basic meaning. But in examples of the first meaning, as…
今週までにはそれを終えてしまいたかったのだが。
or
レポートを終わらせてしまった方が良いよ。
I get a bit of a feeling that しまう is really unnecessary. If しまう isn't going to add any special nuance to the sentence, and is only used for its meaning of "to finish, end something", combining it with 終わる or 終える doesn't seem necessary. It sounds like saying "finish and be done" or something like that (¿?)
I get a bit of a feeling that しまう is really unnecessary. If しまう isn't going to add any special nuance to the sentence, and is only used for its meaning of "to finish, end something", combining it with 終わる or 終える doesn't seem necessary. It sounds like saying "finish and be done" or something like that (¿?)
My understanding (more knowledgeable people please correct me if I'm wrong) is the しまう just adds the nuance of completeness in those so:
レポートを終わらせてしまった方が良いよ
It would be better if the report was completely finished.
If you drop the しまう it would just be:
It would be better if the report was finished.
So, it adds that same nuance that we occasionally use in English between:
I've been digging into this as well. My favorite Japanese grammar textbook gives 完成してしまった as an example in the completed category, so it does seem to be useable with verbs that also contain "finish" or "complete" as part of their meaning.
