Hindley Earnshaw's hatred for Heathcliff had its roots in the fact that his father, Mr. Earnshaw, favored the boy over himself. Hindley had been fourteen years old when Mr. Earnshaw first brought Heathcliff, whom he had found starving in a Liverpool slum, home to live at Wuthering Heights. It was clear from the very beginning that Mr. Earnshaw preferred the young newcomer to his own son, and Hindley reacted with jealousy and a barely suppressed rage. He took every opportunity to torment Heathcliff, and his hatred for the boy was returned in kind. In contrast, Heathcliff developed a special closeness to Hindley's sister Catherine, but although their consuming relationship haunted them both throughout their lives, it never came to fruition. Hindley, with his cruel manipulations, had deprived Heathcliff of any chance he might have had to become an educated man and had forced him to labor as a servant. Hindley effectively managed to turn Heathcliff into someone it would be a disgrace for his sister Catherine to marry.
Hindley was not strong in character. He was cruel and vengeful as a child, and at Mr. Earnshaw's death, he became the master of Wuthering Heights, and ruled with a tyrannical hand. After his wife died, Hindley began drinking heavily, and his personality continued to degenerate. At his lowest point, his old nemesis Heathcliff achieved his revenge, gambling with the drunken Hindley until he won all his possessions, finally becoming himself the master of Wuthering Heights.
Not only does Hindley have and inferiority complex he is also very jealous towards Heathcliff. The inferiority complex would that he thinks he is better than Heathcliff because he is from a well off family, he is not an orphan, and he does not look like a gypsy. Since Hindley's father invest so much time and love into Heathcliff just like he is own natural born son it really makes Hindley mad and jealous that his father is showing so much attention to someone like Heathcliff. There's a point in the book where Mr. Earnshaw says he trust Heathcliff a lot because he tells no lies and Hindley is envious at this unlimited amount of trust Mr. Earnshaw beholds Heathcliff with.