Le Grand Pouvoir Du Chninkel by Jean Van Hamme

In a bleak, mythic world, a humble young man named J’on is chosen by a godlike emissary and granted immense power to become a messianic leader; torn between compassion and the corrupting effects of authority, he leads a desperate uprising against an oppressive empire while confronting the manipulations of gods and the devastating moral costs of salvation, culminating in tragic, ambiguous consequences.