Do you concur with the critic's assessment of Nick's behaviour in the final encounter with Tom? Can you imagine, say, Nick challenging Tom to a duel of honor?
I think that the final encounter with Tom demonstrates to Nick how he needs to go back the Midwest. There is little gallantry and demonstrative valiance that he wishes to display after seeing Gatsby's demise and how everyone abandoned him in the end. Nick is not filled with the demonstrative anger that would compel him to challenge Tom in a duel. Rather, he is disgusted with the life that Tom, Daisy, and Jordan represent:
[T]hey were careless people, [for they] smashed up things and creatures and then retreated back into their money or their vast carelessness, or whatever it was that kept them together, and let other people clean up the mess they had made.
This conclusion of characterization does not reveal an intensity to engage in a dramatic show of force. It is a statement that shows a resignation to disgust without a tinge of melancholy. Nick's reaction to Tom is one in which he recognizes that there can be no duel of honor because honor is not something that Tom represents. There's no point in fighting with Tom. Nick decides to retreat, if nothing else, to save himself from the same condition that engulfed and killed Gatsby. I don't think that the critic's assessment of Nick as challenging Tom to a duel of honor makes sense for Nick has seen the result of romantic and idealistic pursuits in a cold and cynical world. It is for this reason that he wishes to leave it once and for all.