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)...