Differences between なんせ / なにせ / なにしろ / なんにせよ

Question

I just recently posted a question about the meaning of なんせ, and was able to get a better sense of its meaning thanks to the response I received.

In that same post, I learned that なんせ、なにせ、なにしろ、and　なんにせよ all have similar meanings, but cannot be used interchangeably.

I'm curious, what exactly is the difference in nuance?

English translations often show things like 'At any rate' or 'In any case', or if translating from Japanese dictionary, something like 'no matter the circumstances'.

However, it seems to me like there might also be a nuance of giving a reason, almost like a 'because'?

I've come across なんせ and its similar terms used in conjunction with から, だし, and もん, which make me think they might be related somehow. (In the same way that もし and どうやら can be guiding adverbs)

For instance, all these sentences in Attack on Titan follow that pattern:

A:　なんで俺の腕がねえんだ？
^{(Characters' limbs can regrow in this show.)}

B:　そりゃすまん。俺がやったんだ。何せ急いでいたからな。

A:　君たちがここから離れることが必要だと言ったはずだ。

B:　悪かったよ。何しろ心配性なもんでな。

A:　だが 今ある最高の戦力であることには違いない。

B:　ああ、そりゃあ重々承知している。
　　なんせ今回も俺ら調査兵団の作戦は博打しかねえからな。

I'm wondering because in some situations, translating those words as 'At any rate' or 'no matter the circumstances' seems a little odd.

Answer 1

Semantically, なんせ, なにせ and なにしろ are interchangeable. なんせ is most colloquial and informal, while なにしろ is most preferred in formal writing. They are used in the context of emphasizing a reason or important background information, so it's commonly used with から, ので, んで, んだ, のだ, etc. I think the most straightforward translation for them is "after all" or "no matter what".

• 彼はなにしろ忙しいので、返事は来ないだろう。
  He is busy, after all, so I doubt he will respond.
• なにせ時間がないんだ、手短に頼む。
  Anyway, I don't have time, so make it quick.

なんにせよ (or なんにしろ) has an explicit nuance of "whatever", "whether (A or B or...)" or "regardless". It's typically used in the context of having multiple possibilities and making a suggestion/decision. It's similar to どっちにせよ, どちらにせよ, いずれにしろ ("either way", "whichever") except that it can be used when there are more than two possibilities.

• なんにせよ準備は必要だ。
  Either way, we need to be prepared.
• まだ結論は出ていないけど、なんにせよ今日は寝よう。
  We haven't come to a conclusion yet, but whatever it will be, let's go to bed today.
• なんにせよ時間がないんだ。
  Regardless of what it _{(=your opinion, suggestion, etc)} is, I don't have time.

Please read this question and this article for this せよ/しろ.