Scanners III: The Takeover (Scanner Force) (1992)

This is the third in the Scanners series of films, where people have acquired telepathic powers (due to drugs taken by their mothers during pregnancy). This time a brother combats his adopted sister in a telepathic show-down when the sister takes an experimental drug that turns her toward evil. She schemes a plan to take over the world using her psychic powers and must be stopped.