The root of Heathcliff's motivation to take revenge is unrequited love. Though there is great suggestion at the start of the novel that Catherine loves Heathcliff, she can't allow herself to marry below her station. Though she cares for Heathcliff and is loving, she can't offer him the deep sort of love which he desires. Other factors only exacerbate this feeling. Catherine's marriage to Linton, a wealthy neighbor in the countryside, and Catherine's brother who treats Heathcliff very poorly. Upon Heathcliff's return later in life, the other characters are surprised to see that he has become a gentleman. He has returned to buy Wuthering Heights and inflict revenge on those who separated him from Catherine. The separation from Catherine is what motivates him to inflict revenge on the others.
Heathcliff is a character who is tormented by his love for Catherine and by his bitterness over his ill treatment by Hindley. Heathcliff has been treated as a favored son by Mr. Earnshaw, and then after Mr. Earnshaw's death, Hindley exacts revenge on Heathcliff by treating him as a base servant. Heathcliff feels further rage and bitterness when he overhears Catherine tell Nellie that she would be "degraded" by loving Heathcliff. He runs away, filled with hatred for all who have hurt him. When he comes back to Wuthering Heights, he comes back as master of the house, prepared to get revenge on his enemies. After Catherine's death, his bitterness intensifies, causing him to act vindictively and cruelly to the younger generation.
The most important thing that offsets Heathcliff on wanting to seek revenge would be that Catherine's confession to her maid in which she address her want of marrying into status and wealth as opposed to poor life that Heathcliff would give her (cause by Hindley who made him a stable boy and refused him education upon his fathers death). When Heathcliff heard this he decided to runaway and comeback better than his former self and seek revenge on Hindley for treating him so poorly. But when he got back Catherine was married and there was little to do anything about so he felt hopeless and did what he does best... Exact revenge in anyone who was even somewhat connected to his loosing Catherine.
Heathcliff's inner conflictions, pain , frustration lead him to take revenge.
Heathcliff's severe pain for cathy his beloved made him to take revenge . There were still more reasons of his revenge like- Hindley's torture etc but the main and ultimate reason was his beloved cathy.
Heathcliff's revenge is cuased by his past experiences that he had faced during the time that he was living at the heights prior the death of Mr.Earnshaw.
The past experiences can be seen as such Hindley contious ill-treatment and the Lintons scorn of him.
Heathcliff loved cathy`she 2 loved him`but she said she could not marry him because it would degrade her status`and because Heathcliffs education was stopped by HINDLAY,he did not get a chance to raise his social class`,so CATHY married edgar and Heathcliff was left alone. he would have not mind the beating or ill treatment by Hindlay but seperation from cathy was 2 much for him, so he decided to take revenge from the people who took cathy away from him
In the novel Wuthering Heights, Heathcliff plays the lead role as a villain and a romantic hero with a forbidden and tormented love to Catherine Earnshaw. Throughout the course of the novel he had many changes in his social status from being a orphan beggar in the street to a gentlemen and then again to a common labourer and once again to a gentlemen. He seeks revenge may be because he was bullied by Master Hindley while he was at the Heights and also maybe because he lost his love due to the fact the Hindlry degraded him in the household which made catherine choose Edgar Linton over him. In the later part of the novel his revenge normally shown in used towards Hindleys son and other younger generations including his own son. Heacliff turned from being a innocent youth to a evil revengful man due to his contant degrading and his lost love and he seeks revenge to satisfy his anger and bitterness that was caused by other in the novel.