In F. Scott Fitzgerald's novel, "The Great Gatsby," Nick finally shakes hands with Tom when he comes to understand that Tom cannot be held responsible for his own callousness. Having already made up his mind to leave the East Coast for the Midwest, Nick understands that Tom, along with his other friends, has been corrupted by East Coast values.
Tom's callousness manifests in a number of ways throughout the novel, but his unavailability to attend Gatsby's funeral has the greatest impact on Nick. In fact, Nick was the only one of Gatsby's close friends to attend the funeral, having arranged it himself. The only other people who attended were Gatsby's father, a few servants and "Owl Eyes" (who arrived late).