Famous for the assassination of Rasputin, which he may or may not have actually had a hand in.
On a lighter note, he was also responsible for the familiar disclaimer on books and movies, this is a work of fiction, any resemblance to persons living or dead is purely coincidence.
It all had to to with the 1932 MGM rather ahistorical production, Rasputin and the Empress, in which a “fictional” Prince Chegodieff is credited with killing the Mad Monk after the fellow had hypnotized and raped Chegodieff’s wife, the Princess Natasha.
Yusupov had no problem with being thought the killer of old Creepy-Drawers, but the bit about the rape was, to his mind, libelous. The British courts agreed and MGM settled for £25,000, the removal of some crucial footage in the first reel, and the disclaimer at the start of the film.
But wait, there’s more. Turned out that there was a real Prince Chegodiev, who also sued on grounds of libel. And also won.
Not easy, the movie making business.
(For footnote minded people like me, the question remaining is, is Chegodiev the Prince Alex Chegodiev mentioned here, or his son Paul, or someone else entirely? If one of the above, it clearly did nothing to turn other family members off of the film industry. )