Throughout Wuthering Heights two distinct yet related obsessions drive Heathcliff's character: his desire for Catherine's love and his need for revenge. Catherine, the object of his obsession, becomes the essence of his life, yet, in a sense, he ends up murdering his love. Ironically, after her death, Heathcliff's obsession only intensifies.
Heathcliff's love for Catherine enables him to endure Hindley's maltreatment after Mr. Earnshaw's death. But after overhearing Catherine admit that she could not marry him, Heathcliff leaves. Nothing is known of his life away from her, but he returns with money. Heathcliff makes an attempt to join the society to which Catherine is drawn. Upon his return, she favors him to Edgar but still he cannot have her. He is constantly present, lurking around Thrushcross Grange, visiting after hours, and longing to be buried in a connected grave with her so their bodies would disintegrate into one. Ironically, his obsession with revenge seemingly outweighs his obsession with his love, and that is why he does not fully forgive Catherine for marrying Edgar.
After Catherine's death, he must continue his revenge — a revenge that starts as Heathcliff assumes control of Hindley's house and his son — and continues with Heathcliff taking everything that is Edgar's. Although Heathcliff constantly professes his love for Catherine, he has no problem attempting to ruin the life of her daughter. He views an ambiguous world as black and white: a world of haves and have-nots. And for too long, he has been the outsider. That is why he is determined to take everything away from those at Wuthering Heights and Thrushcross Grange who did not accept him. For Heathcliff, revenge is a more powerful emotion than love.