Nick Carraway is a character with both strengths and weaknesses. Though he is strong enough to attempt to be his own person while those around him pursue conformity and try to fit into prefabricated identities, he nonetheless stands in constant judgement of Gatsby - the one character who achieves some individuality in the small world of the novel.
Nick is, then, a man between weakness and strength as we meet him in the novel; not yet completely formed. The book is, among other things, a coming of age story for Nick Carraway.
The most commonly discussed weaknesses of his character relate to his judgemental nature. Nick introduces himself as someone who refrains from judging others, yet as a narrator judgement is a rather constant habit for Carraway. Though Nick claim to be the only honest person he knows, the reader knows that clearly he is not completely honest with himself.
Furthermore, Nick is attracted to Jordan. He identifies with her. We can see his own weakness in his identification with Jordan Baker.
While he is physically attracted to Jordan, he recognizes her basic dishonesty and inability to commit to a relationship.
Jordan proves to be a moral coward in the end and though Nick ultimately proves himself to be better than a coward, he is content to go along as part of a pair with Jordan, a cheater and a gossip.
Nick, like Jordan, participates in the society that he also judges, bringing his integrity into question. However, in the end, Nick breaks ties with Jordan and sides with Gatsby. He is the only character to do so. Nick finally sees value in Gatsby's willingness to dream.
His ignorance of his real greatness and misunderstanding of his notoriety endear him to Nick, who tells him he is better than the “whole rotten bunch put together.”