English and Japanese help please
 

I was reading this book where I found the phrase 負け惜しみの強い方 I couldn't figure out at first what the strong person was possessing, but after looking around I found out it is a set phrase for someone who makes excuses.
But in every dictionary I look up, I find the translation eat sour grapes. What it means?

Easy for someone who isn't a native English speaker to be confused by this. "To eat sour grapes" means "to be a sore loser." A sore loser is someone who not only loses, but behaves badly afterward; more often than not, this includes saying things like "I could have won, but my opponent cheated." That is an excuse.

So the two translations are not that different.

Personally, I'd just leave it as the "sour grapes" translation. That's what I learned it as. Plus it's more accurate IMO. 負け惜しみ is not just making excuses, but could be throwing a computer after losing an online match, yelling at your coach for not being a good enough coach, etc.

And to break the words down:
負け惜しみ is "lose" + "regret/rue/begrudge" so it makes sense that it has something to do with behaving in a negative way after losing.

強い = strong

方 = one/person

So "one with a severe case of sour grapes" would be how I translate it.