I am wondering if Beria truly was likely guilty of being the mass murderer, pedophile, and rapist he was accused of, or if after Stalin's death, he functioned as a convenient scapegoat for blame as the country went through De-Stalinization.
One view of the events is presented in the top answer of this thread:
...ironically by a user with a deleted account.
Beria was definitely a mass murderer and most likely a rapist as well, even if his crimes were at times exaggerated or overemphasised for propaganda purposes.
Beria the mass murderer
Beria can under many definitions of the term be called a mass murderer and he was despised for it by his colleagues. As leader of the NKVD after 1938 he was responsible for countless atrocities. Some of the most famous are the Katyn massacre (the murder of nearly 22,000 polish prisoners of war), the mass deportations of so called “enemy nations” during WW2 who were accused of collaborating with the invading Nazis such as the Chechens, the purge in the red army of those considered politically unreliable and the horrific living conditions that existed in many Gulags. Beria was also heavily involved in the purging of high ranking members of the party in incidents such as the “Leningrad Affair” in which prominent members of the Leningrad party organisation were arrested, put on trial on trumped up charges and executed. The secret police of which he was head frequently tortured suspects to force them to confess, often to wildly implausible charges. This is probably the easiest part of your question to answer as Beria’s guilt is completely clear, if you want you can find the documents authorising some of these massacres with his signature on them online.
Beria the coward and opportunist
Beria was not a man who can be described as having firm principles that he stuck by. In an interview many years later his former colleague Molotov the USSR’s foreign minister who had joined the plot to have him arrested stated
“I considered then, and still consider, Beria to be an unprincipled man. He was a careerist engaged only in what was to his advantage. He was not even a careerist, or, so to speak, merely a careerist since he did not address most issues from a Bolshevik perspective.
He killed a lot of people.
I don’t think Beria was the principal culprit. He destroyed people for personal rather than party-related motives. That’s possible. He was unprincipled. He was not even a communist. I consider him a parasite on the party. … In my opinion there were excesses, but these excesses were brought about by Stalin. Beria himself was very much afraid of Stalin.”
In this conception of Beria he is described as fundamentally unprincipled, killing people out of personal enmity, a desire to gain power and a terrible fear of Stalin rather than out of a devotion to communism and the Soviet Union. Even more interesting is that Molotov did not consider all heads of the secret police to have displayed a similar lack of principle. The first, Felix Dzerzhinsky is described by him as “a radiant, spotless personality”, his successor Yagoda is addressed in terms even nastier than Beria, being called “a filthy nobody who wormed his way into the party and was only caught in 1937”. The man whose job Beria took, Yezhov Molotov has a great deal more sympathy for, with Molotov describing him as loyal and hardworking but as having “overdone it” during the Great Purge. Beria in Molotov’s conception was very competent but fundamentally unprincipled, an account of Beria that matches with what we know of Beria’s behaviour after Stalin’s death.
As the historian Sheila Fitzpatrick notes “the speed of the reform legislation in the next few months (after Stalin’s death) owed a great deal to Beria’s frenzied pace. Within six weeks, as head of the security police, he had released the Jewish doctors, investigated Mikhoels’s death and informed the team of Stalin’s involvement, forbidden the use of torture in interrogations, transferred much of the MVD’s industrial empire to civilian ministries, and set in motion the release of more than a million prisoners from Gulag.” The man who had presided over the Gulags for over a decade and had ordered tens of thousands tortured and executed suddenly reversed himself as soon as his old master was gone. During that period his ambition, and perhaps more importantly what his comrades regarded as an utter lack of principles became increasingly apparent. After demonstrations against communism in East Germany Beria called for an end to the attempted construction of socialism in the country. “Socialism? What socialism? We should stop chattering mindlessly about socialism in Germany!” he shouted, to the dismay of his comrades. Khrushchev in his memoirs also says that on the night before Beria’s arrest Beria boasted that they would ensure that their children live like kings and restore private property in the USSR for their children, hardly a communist dream for the future.
Beria the rapist
Beria’s many rapes became an important part of the propaganda against him. Some, like you are sceptical of the extent of the charges laid against him. To quote Fitzpatrick again “Many other people, both associates and victims, gave testimony as well, and the scenario that emerged, as in the Zhemchuzhina case back in 1949, came to focus on his sex life, with lurid allegations of multiple rapes, forcible abduction of young women from the street, and so on. Although this subsequently entered into Soviet folklore, the story of Beria as a sexual predator seems, though not wholly unfounded, to have been wildly exaggerated. His own account under interrogation of how he conducted his relations with the women he had affairs with, including a young one picked out on the street for him by a subordinate, is basically supported by that of a singer claiming to have been his mistress, after catching his eye during a performance, who described seduction (admittedly under intimidating circumstances) rather than rape.”
Personally, I am however somewhat sceptical of Fitzpatrick’s argument here. Seduction under intimidating circumstances by a man who has the power of life and death over you and your family, especially if you have been selected as a potential object of affection by one his subordinates does not to my mind allow for consent. Could any of these women actually have said no without fearing for their own and their families safety? Similarly the fact that the states case against Beria did not rely on arguing that Beria was a rapist (treason, which is the main thing he was charged with was more than enough to get you executed) and the fact that we have accounts that many prominent officials warned their daughters and wives not to go alone into the same room as the man suggests to me that he was in fact a sexual predator, if one whose crimes have possibly been exaggerated for political purposes.
Beria the scapegoat
Beria was however also a scapegoat for crimes committed under Stalin. But that does not make it that he was innocent or even necessarily less guilty than presented in all matters. The truth often makes for the best propaganda, and newspapers could with complete truthfulness report on the massive purges Beria under Stalin’s orders and/or encouragement carried out whilst at the same time delicately avoiding the topic of say the purges Khrushchev carried out in Ukraine. Once the propaganda machine really got going Beria’s reputation, never that great outside to start with was pitch black, with one anonymous writer for example asking “Could he be hung?” hopefully. There were still those who maintained his innocence to some extent. Beria’s son Sergo Beria (interesting fact, Stalin’s daughter was once in love with Sergo only for Sergo’s father to end the relationship out of fear that Stalin would begin interfering in their family life) published a book describing his father as a man of culture and science who was unfairly betrayed by his colleagues who also share the blame for the many mass killings that occurred under him. In a similar vein Sergo denies that his father raped anyone. However, it is impossible to deny many of the crimes the man committed (his signature is on the documents ordering many of them to be carried out) and in the end Sergo's defence of his father fundamentally rings hollow, as other people also committing crimes in no way exonerates Beria.
So yes, Lavrentiy Beria was a mass murderer and most likely a rapist as well, even if his crimes were at times exaggerated or overemphasised for propaganda purposes.