What does Tom's behavior reveal about his character?

Throughout the novel, Tom's behavior reveals him to be egotistical, brutal, and self-centered. Wherever he is, misery seems to follow. Even Gatsby's wild parties lose their luster when Tom shows up.
We have to keep in mind that we are seeing Tom through Nick Carraway's eyes, and Nick hates Tom. Nevertheless, Tom's own behavior condemns him. He shows his egotism in his endless assumption of his own superiority: he is a "Nordic," and this, in his mind, gives him the right to pass judgment on everyone else. He shows his arrogance when he rides off on horseback with his friends rather than wait for Gatsby to get his car so he can join them for dinner. Tom thinks that Gatsby should simply know he isn't wanted by Tom's "set."
Tom reveals his brutality when he both bruises Daisy's finger and breaks Myrtle's nose by hitting her in the face. He shows his self-centeredness when he insists on having affairs from early on in his marriage, despite this hurting Daisy. Wherever he is, be it hosting Jordan and Nick during dinner at his home, being part of the party at Myrtle's New York apartment (which he pays for), or spending an afternoon at the Plaza, he seems to enjoy insulting people.
Tom plays with George Wilson, pretending Gatsby's car is his own and offering to sell it to him (and, of course, having an affair with George's wife right under his nose). He shows no remorse over Gatsby's death (he says that Gatsby "had it coming") and none over George's either. He, like Daisy, is willing to run away from the problems he's created and let other people clean up the mess.

In Chapter 1, Nick Carraway arrives at Daisy and Tom Buchanan's home to visit them on their gorgeous estate in the East Egg. Nick initially describes Tom as having "arrogant eyes" and a "cruel body." Tom is depicted as a rather unintelligent, cocky man, who exudes masculinity and authority. Nick mentions that Tom speaks with a sort of "paternal contempt" and carries himself with a sense of superiority. After talking about his magnificent estate, Tom takes Nick inside to talk to Daisy and Jordan. During their conversation, Tom begins to discuss his racist ideology by bringing up a book entitled The Rise of the Colored Empires. Tom attempts to appear intelligent and educated but comes across as simple, prejudiced, and angry. Tom then gets up to answer the phone, and the ladies inform Nick that Tom is speaking to another woman. The fact that Tom does not attempt to conceal his affair is rather telling and portrays him as a callous, insensitive man. Overall, Tom's behavior reveals his selfish, immoral personality and lack of self-awareness.