Fan Casting Shazam! (Horror Movie)

Young teenager Billy is kidnapped by a deranged satanist that conducts a ritual on him, this ritual allows a spirit to possess Billy with their lightning powers. While also transforming him into a fully grown, towering man. Billy is initially horrified by the situation, but he eventually finds himself more than happy to stay in this form forever. Eventually he decides to take over the world, seeing everyone else as beneath him.