How to say “Fastest by a large margin”?

Let's say there is a 1km race, and here is the ranking:

A: 170 seconds
B: 301 seconds
C: 308 seconds
D: 312 seconds

We can say that A is fastest by a wide margin, because he was much faster than all other runners.

How to say fastest by a large margin in Japanese?

Adapting from ALC, I wrote `大幅に一番速い`, but a Japanese colleague taught me that `大幅` and `一番` can not be used at the same time. She advised me to use only one or the other, but I feel that the idea I want to convey (much faster than all others) is lost.

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If you think about it 大幅に一番～ doesn't really make sense since 大幅 refers to a large span and 一番速い refers to the singular fastest. As such we need an expression that emphasizes the difference.

Looking at alc for some similar phrases, I found some stuff that might work. Checking "by a long shot" gives us the following:

・This one is better by a long shot. : こちらの品の方がはるかに良いです。

This seems appropriate to me for your situation. 大きく差をつけて makes perfect sense since we refer to an outstanding thing by saying 差がつく. 断然 also works with a meaning like "firmly" in terms of an extent or certainty. The example sentence uses はるかに, which you can also translate as being something like "a distant first."

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「一番早い」 means "earliest".「一番速い」 means "fastest". – ramsay Oct 3 '13 at 14:54
sorry, just a 変換ミス – ssb Oct 4 '13 at 6:07

I think a more colloquial way is: 「彼は他の人よりも、めちゃくちゃ速かった。」 "He was absurdly faster than anyone else." But, writing "めちゃくちゃ" might be unnatural because there is so much kana. Spoken though, "めちゃくちゃ" sounds pleasant/natural in my opinion.

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You can use ぶっちぎり, which kind of means "overwhelming" with a nuance of competition.

• ぶっちぎりの速さでトップフィニッシュ
• ぶっちぎりで優勝した

"Fastest by a large margin" would be ぶっちぎりの速さ.

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How about `大差で【たいさで】`? It looks like you could say:

• 大差で勝つ　　　　　　Win by a large margin
• （誰かを）大差で破る　Beat (someone) by a large margin

Neither of these examples directly expresses fastest, though.

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