Yes, Kazuya Mishima did throw Jin Kazama off a cliff in a specific secret ending of the fighting game Tekken 8.
This dramatic turn of events is depicted in one of the alternate conclusions available in the acclaimed fighting game. In this particular scenario, following a brutal confrontation between the father and son, Kazuya asserts his dominance by throwing Jin off a cliff. This intense moment underscores the deep-seated rivalry and animosity that defines their relationship within the Tekken universe. It serves as a stark, albeit non-canonical, resolution to their long-running conflict, showcasing the ruthless nature of Kazuya.
For more information about the game and its storyline, you can visit the official Tekken 8 website.