1. Zhang Xiaofan violated their agreement: in the novel, Zhang Xiaofan, as the master of Wang Zongjing, originally agreed to enter the immortal door of the right path together. However, Zhang Xiaofan was possessed in the later period, fascinated by the methods of magic teaching, and finally fell into the magic way, which made Wang Zongjing feel very angry and disappointed.
Zhang Xiaofan's behavior made Wang Zongjing feel betrayed: Wang Zongjing regarded Zhang Xiaofan as a friend and mentor, and he could not accept Zhang Xiaofan's betrayal. In Wang Zongjing's view, Zhang Xiaofan's behavior not only violated their agreement, but also betrayed his beliefs and values, which made him hate Zhang Xiaofan.
3. Zhang Xiaofan's position makes Wang Zongjing feel threatened: in the novel, Zhang Xiaofan, as a former sect leader, poses a threat to Wang Zongjing and his forces. Therefore, Wang Zongjing's resentment against Zhang Xiaofan may also be related to this conflict of power and interests.
Generally speaking, Wang Zongjing hates Zhang Xiaofan mainly because Zhang Xiaofan violated their agreement. His behavior made him feel betrayed, and his position posed a threat to Wang Zongjing's interests.