Love is a two way street. In order for love to work it must be given and returned. If love is left unfulfilled it can lead a person to be spiteful, vengeful, and at the extreme villainous. In Emily Bronte's novel, Wuthering Heights, Heathcliff is the villain because he is frustrated about his unrequited love for Cathy. Heathcliff's villainy is apparent in how he treats the Earnshaws, degrading Hindley and Hareton just as Hindley did him. This is also shown in his actions against the Lintons. Heathcliff hates the Lintons because Cathy married Edgar. Heathcliff uses his treachery to steal away the Linton fortune and to degrade their offspring. Heathcliff's villainy is finally shown in how he treats Cathy herself. He loves her so much he hates her. He feels that Cathy betrayed her heart and married Edgar. Heathcliff as the villain is first shown in his actions against the Earnshaws.
When Heathcliff returns to Wuthering Heights after several years, his frustration leads him to exact revenge on Hindley Earnshaw. Heathcliff blames Hindley for Cathy not returning his love and becoming married to Edgar. Hindley reduced Heathcliff to such a status that it would ruin Cathy to marry him. Heathcliff's villainy is shown when he returns the favour to Hindley, reducing him and his son Hareton to servant class. This is apparent when Heathcliff is talking to Nellie about his joy in degrading Hareton, he says,
I've pleasure in him!...He has satisfied my expectations - if he were born a fool
I should not enjoy it half so much - But he's no fool; and I can sympathise with
all his feelings, having felt them myself - I know what he suffers now, for instance exactly - it is merely a beginning of what he shall suffer though. And he'll never
be able to emerge from his bathos of coarseness, and ignorance. I've got him
faster than his scoundral of a father secured me, and lower; for he takes a pride
in his brutishness. (252-253)
This is also shown when Heathcliff accidentally saves Hareton from certain death. This is apparent when Nellie says, "A miser who has parted with a lucky lottery ticket for five shillings, and finds next day he has lost in the bargain five thousand pounds, could not show a blanker countance than he did on beholding the figure of Earnshaw above - It expresses...the intense anguish at having made himself the instrument of thwarting his own revenge."(Bronte, 115) These quotes clearly show Heathcliff's villainy through his actions towards the Earnshaws. Heathcliff is also shown as the villain by his vengeful actions against the Lintons.
Cathy married Edgar Linton for his status and wealth, betraying her love for Heathcliff. Heathcliff is so frustrated that Cathy married Linton that he seeks to...