Bela Abzug. I have not thought of her in years. She was an extreme communist Marxist, back in the day when the FBI actually kept people like that under surveillance and not promote them to head the Bureau. The biggest problem is she would be considered a moderate today.
It was John Brennan of the CIA I was thinking about, not the head of the FBI, some of them have likely been/are communist too.
https://spectator.org/john-brennans-president-remembering-comrade-gus-hall/