The image that has stuck in my mind is when Nick first describes Tom to the readers. Relating that Tom had been a big deal in college sports and had reached his personal best during that time. Now, he “would drift on forever seeking, a little wistfully, for the dramatic turbulence of some irrecoverable football game.” Nick's first sighting of him when he goes to tea is the image of Tom, "Standing in riding clothes with legs apart, he appears aggressive, supercilious, “with a touch of paternal contempt,” .
Tom's need to appear imposing when Nick comes to visit is a clue to his pesonality throughout the novel.
There are probably a number of statements Nick makes about Tom, but the most meaningful to me is in the Chapter Nine, where Nick finally reaches an epiphany about Tom, and Daisy as well. He says:
"I couldn't forgive him or like him but I saw that what he had done was, to him, entirely justified. It was all very careless and confused. They were careless people, Tom and Daisy-- 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...
I shook hands with him; it seemed silly not to, for I felt suddenly as though I were talking to a child."