Svengali comes to mind. Svengali was a very famous (and fictional) opportunist who seduced and dominated a young girl named Trilby. But she was his only victim. So, Svengali doesn’t make the cut.
Rasputin comes to mind. Grigori Rasputin was a very famous peasant of late Tsarist Russia who had enormous influence over the Court in pre-revolutionary Russia. But his power was short-lived. So, no, Rasputin doesn’t make the cut.
The great Mesmer comes to mind. Franz Mesmer was a German physician who is credited with inventing (or discovering) hypnotism. So feared was he in his day that the word Mesmerism pre-dated the first use of the word hypnosis by nearly 100 years. I don’t know, is Mesmer the real deal?
But surely Grover Norquist is the real deal.