A man of brute strength and power, arrogant and malicious, Tom Buchanan is clearly the villain of Fitzgerald's The Great Gatsby. Very self-absorbed and proud of his wealth and the power it brings, Tom Buchanan haughtily displays his property to Nick Carraway, explaining that he has had his polo ponies brought from the wealthy Chicago suburb of River Forest to East Egg. His wife Daisy, whom he has purchased with an expensive necklace, is mere property to him, too, as he thinks nothing of receiving phone calls at home from his mistress Myrtle Wilson. Yet, he is angered when Daisy presumes to love Gatsby.
With much duplicity of character, although he has a mistress, Tom announces that he has had Gatsby's background investigated and asks Gatsby "what kind of a row" he tries to cause in his house. And, when Daisy tells him to have some self-control, he retorts,
"Self control!...I supppose the latest thing is to sit back and let Mr. Nobody from Nowhere make love to your wife. Well, if that 's the idea you can count me out..."
Above all else, Tom Buchanan is villainous because he destroys Jay Gatsby and his romantic dream. For, he conspires with Daisy to allow Mr. Wilson to believe that it has been Gatsby himself who has driven the "yellow death car" that has stricken Myrtle, rather than Daisy.
Labeled by Nick as a "careless person" Tom Buchanan
smashed up things and creatures and then retreated back into [his] money or...vast carelessness...and let other people clean up the mess....
A selfish brute, Tom Buchanan represents the self-centered, amoral, and supercilious wealthy of the East Coast that Fitzgerald himself encountered and found reprehensible in their conduct.
Tom who is not an appreciable character in the story, does become the villain in certain parts of the story.
Firstly he shows his real colour when he keeps Myrtle and he has that guts to take Nick;the cousine of his wife to meet 'his girl'.
Seconly when he breaks the nose of Myrtle in front of everybody in their apartment during the party.
Then when he tries to insult Gatsby in front of Daisy and when he brings Gatsby's true olour in front of everybody(Daisy,Nick and Jordan) that is he is a bootlegger.This is where Daisy learns about his reality and decides to leave him.It is because of Tom that Gatby's dream remains incomplete.
And finally in the end when Tom tells George that Gatsby was driving the yellow car(even though its not Tom's fault).This is where Tom is partly responsible for Gatsby's death.