From the afterword of Hard to be a God:
On the advice of I. A. Efremov, we renamed the Minister of the Defense of the Crown Don Reba (he had previously been Don Rebia—an overly simple anagram, in the opinion of Ivan Antonovich.)
While I enjoy anagram puzzles, I wasn't even going to attempt one in not only a foreign language but a less familiar alphabet, so I remained puzzled about what anagram this was referring to, until @Gilles pointed out in chat that of course Rebia (Ре́бия) would have been an anagram of Beria (Бе́рия), the most famous and long-standing chief of the Soviet secret police. The reference is clear: Don Reba is also a chief of secret police, also ruthlessly responsible for the detection and punishment of thousands of so-called traitors.
Other than the name, what similarities can be drawn between the character of Don Reb(i)a and the real-world figure of Beria? I'm interested to see how far the comparison goes, and how clear it is from the text of the novel, without using anagram games, that Don Reba was based on Beria.