Aaaa I deleted my long-ass reply

Gimme like an hour or two to get off mobile and give you a quality answer.

Quick answer is: a lot of mystery is around beria that's still locked away in the soviet archives, and realistically the best way to gage him would be in the writings of those who were around him during the time he was alive. I'm keeping an equally open mind on him as I do with other Soviet leadership.

Okay I hope you like reading.

Beria wasn't Stalin's first pick for the Job Beria would later assume

In the fall of 1938, when the question arose of removing Yezhov from his position at NKVD, Stalin proposed the candidacy of Malenkov as the new Commissar of Internal Affairs. But the majority of the Politburo recommended Beria for the post.

Getty and Manning. Stalinist Terror. Cambridge, NY: Cambridge University Press, 1993, p. 38

The Russian historian Boris Starkov has recently written that in Politburo meetings during August 1938 Zhdanov and Andreev stressed the poor quality of party cadres promoted during the mass repressions. Soon Kaganovich and Mikoyan joined them “against Yezhov.” Then in the fall, according to Starkov, Stalin proposed replacing Yezhov with Malenkov. But the rest of the Politburo blocked the Gensec and insisted on Beria, though why is not clear.

Thurston, Robert. Life and Terror in Stalin’s Russia, 1934-1941. New Haven: Yale University Press, c1996, p. 131

One of Stalin's last living bodyguards liked Beria as much as he liked Kruschev

How can anyone now allow himself the stupidity of criticizing Stalin for repression and crimes? This was a psychosis that was cleverly instituted by Yezhov and other enemies of the State… this psychosis took over the minds of millions of people. Practically all were involved in looking for “enemies.” The Central Committee ACP[B] was against this, fought this tooth and nail—Stalin in particular. People got involved in this, and friends were “drowning” friends in the name of getting rid of “enemies.” Of course, this cannot all be explained as a mass psychosis! In all the examinations that were conducted into this period, we had 30-40 people going over the same documents, but NOWHERE did we EVER find the name of Stalin, or the command of Stalin, or the resolution to do these things which were undertaken by the REAL ENEMIES of the Soviet people. No directives either of Stalin, Molotov, or Voroshilov were to be found in all of these documents. According to my way of thinking, Stalin also bears some blame because he was the Head of the Motherland. His fault was that he was always favoring “collective decisions” and thus was fooled by his “comrades-in-arms.” Yagoda, Malenkov, Khrushchev, Beria, and others. Yezhov, Stalin spotted from the start and took steps to stop him and get rid of him.

Rybin, Aleksei. Next to Stalin: Notes of a Bodyguard. Toronto: Northstar Compass Journal, 1996, p. 80

It was likely that Beria played a key role in stopping the greatest excesses of the Ezhovshchina

Beria boldly told Stalin that Yezhov, who had succeeded Yagoda the year before as Chief of the Commissariat of the Interior…had passed all bounds of reason and discrimination in his conduct of the Purge;…

Duranty, Walter. Story of Soviet Russia. Philadelphia, N. Y.: JB Lippincott Co. 1944, p. 229

Early in 1938, however, Stalin became disturbed by the mounting fury of the Ezhovshchina. His purpose of liquidating the old Bolsheviks and the veterans of the Revolution and the Civil War, and other sources of opposition, had been achieved. But under Yezhov the purge had spread like a malignant plague. Everywhere people were spying and informing against each other and everywhere arrests were on the increase. Terror was raging out of control. Stalin saw the need to call a halt. He showed the same sense of timing and the same authority, which he had displayed nearly eight years earlier with his article “Dizziness From Success.” In January 1938 a central committee passed a resolution which heralded what was to be called the “Great Change.” The title of the resolution was “Concerning the Mistakes of Party Organizations in Excluding Communists from the Party, Concerning Formal-Bureaucratic Attitudes Towards the Appeals of Excluded Members of the Bolshevik Party, and Concerning Measures to Eliminate These Deficiencies.” The new orders were passed quickly to the party secretaries at every level and to the command points of the NKVD, and emanating from the Kremlin in Moscow. They were promptly obeyed. The new enemy was identified now as the Communist-careerist. He had taken advantage of the purge to denounce his superiors and to gain promotion. He was guilty of spreading suspicion and of undermining the party. A purge of careerists was launched. At the same time mass repressions diminished and the rehabilitation of victimized party members began. The real halt to the great purge came, however, in July 1938, when Beria was appointed Yezhov’s deputy. He took charge of the NKVD at once, although Yezhov was not removed until December 1938, when he was made Commissar for Inland Water Transport. Soon afterwards he was shot. Many NKVD officers were tried and executed for extracting confessions from innocent people, while others were relegated to labor camps. Loyal party members, emerging from the long nightmare, were relieved by the purging of the NKVD. It confirmed their belief that fascists had insinuated themselves into the security forces and the government and that they were responsible for the cruel persecutions and injustices of the Ezhovshchina. This explanation was encouraged officially, and it absolved Stalin and the Politburo of responsibility. Directly controlling every branch of Soviet society and deeply involved in the buildup of the armed forces and conduct of foreign policy, Stalin could not maintain detailed control over the purge. He was aware that the NKVD had arrested many who were not guilty and that of the 7 to 14 million people serving sentences of forced labor in the GULAG camps many were innocent of any taint of disloyalty…. He resented this waste of human material. The aircraft designer Yakovlev recorded a conversation with him in 1940, in which Stalin exclaimed: “Yezhov was a rat; in 1938 he killed many innocent people. We shot him for that!”

Grey, Ian. Stalin, Man of History. London: Weidenfeld and Nicolson, 1979, p. 288

Also some reading on Stalin in Moscow.

Stalin stayed in Moscow. On November 7, 1941, while German guns roared in the suburbs and Hitler announced Moscow already taken, Stalin reviewed the troops in Red Square.

Strong, Anna Louise. The Stalin Era. New York: Mainstream, 1956, p. 98

In his memoirs, Khrushchev portrays Stalin’s panic and confusion in the first days of the war and later. I saw no such behavior. Stalin did not isolate himself in his dacha until June 30th, 1941. The Kremlin diary shows he was regularly receiving visitors and monitoring the deteriorating situation. From the very beginning of the war, Stalin received Beria & Merkulov [cohead of the Soviet security service] in the Kremlin two or three times a day. They usually returned to NKVD headquarters late at night, or sometimes called in their orders directly from the Kremlin. It appeared to me that the administrative mechanism of command and control was functioning without interruption. In fact, Eitingon and I maintained a deep belief in our ultimate victory because of the calm, clear, businesslike issuance of these orders. On Nov. 6, 1941, I received an invitation to attend the October Revolution anniversary gathering in the Mayakovsky subway station. Traditionally, these celebrations were held in the Bolshoi Theatre, but this time, for security reasons, it was arranged on the subway platform. … Stalin spoke for about 30 minutes. I was deeply moved, because his confidence and self-assurance symbolized our ability to resist the Germans.

Sudoplatov, Pavel. Special Tasks. Boston: Little, Brown, c1993, p. 134

This excerpt from Izvestia, #6, 1990 confirms Sudoplatov’s contention that Stalin, contrary to Khrushchev’s claims in his memoirs, was not immobilized by panic after the German invasion of the Soviet Union on June 22nd, 1941, but rather received a steady stream of visitors at his Kremlin study.

Sudoplatov, Pavel. Special Tasks. Boston: Little, Brown, c1993, p. 433

It is worth recording Dimitrov’s attitude toward Stalin. He, too, spoke of him with admiration and respect, but without any conspicuous flattery or reverence…. He recounted: “When the Germans were outside Moscow, a general uncertainty and confusion ensued. The Soviet government had withdrawn to Kuibyshev. But Stalin remained in Moscow. I was with him at the time, in the Kremlin. They were taking out archives from the Kremlin. I proposed to Stalin that the Comintern direct a proclamation to the German soldiers. He agreed, though he felt no good would come of it. Soon after, I too had to leave Moscow. Stalin did not leave; he was determined to defend it. And at that most dramatic moment he held a parade in Red Square on the anniversary of the October Revolution. The divisions before him were leaving for the front. One cannot express how great a moral significance was exerted when the people learned that Stalin was sitting in Moscow and when they heard his words. It restored their faith and raised their confidence, and it was worth more than a good-sized army.”

Djilas, Milovan. Conversations with Stalin. New York: Harcourt, Brace & World, 1962, p. 37

Moscow was bombed by German aviation. Panic began to seize the city’s population. The Nazis were only 80 kilometres away. Part of the administration was evacuated. But Stalin decided to remain in Moscow. The battles became more and more fierce and, in early November, the Nazi offensive was stopped. After consulting with Zhukov, Stalin took the decision to organize the traditional November 7 military parade on Red Square. It was a formidable challenge to the Nazi troops camped at the gates of Moscow. Stalin made a speech, which was broadcast to the entire country.

Martens, Ludo. Another View of Stalin. Antwerp, Belgium: EPO, Lange Pastoorstraat 25-27 2600, p. 247 [p. 224 on the NET]

[In September 1941] The situation at the front is bad…. If it becomes necessary to abandon Moscow we can’t be sure that [the leadership will stand firm–implied]…. In the Instantsia they are not quite sure either that [Stalin will stand firm–implied]…. Stalin stands for war to the end…. While with others…Brest-Litovsk is in the air.

Litvinov, Maksim Maksimovich. Notes for a Journal. New York: Morrow, 1955, p. 307

We must get the peasant going and instill in him the hatred of the enemy…. What a brilliant order of Stalin’s to the Army…. “A fighter should not die without leaving the corpse of a German interventionist by his side. Kill him with a machine-gun, or rifle, a bayonet…. If you’re wounded, sink your teeth into his throat and strangle him as you would a wild beast”.

Litvinov, Maksim Maksimovich. Notes for a Journal. New York: Morrow, 1955, p. 309

The main blow was aimed directly at the capital, Moscow, whose outskirts were reached by late fall. Almost all the government offices had been evacuated to the east. But Stalin remained in the capital, where he assumed personal command of the war. On Dec. 2, 1941, the Nazis were stopped in the suburbs of Moscow. In December 6, Stalin ordered the first major counterattack to occur in World War II.

Franklin, Bruce, Ed. The Essential Stalin; Major Theoretical Writings. Garden City, New York: Anchor Books, 1972, p. 31

As to Stalin’s nerves, or lack of them, his generals make no criticisms. Rather, Marshal Zhukov told a war correspondent that Stalin had ‘nerves of steel’. The correspondent, author Ehrenburg, wrote that the Marshal repeated these words to him several times when they met at a command post near the front line early in the war. Even General Vlasov who had a great grievance against Stalin and, therefore, cause for resentment, told the Germans upon his capture that Stalin had strong nerves. Speaking to Dr. Goebbels, the Nazi Minister of Propaganda, he said that in the autumn of 1941, when the city of Moscow was threatened by advancing German armies, every one in the Kremlin had lost his nerve but only Stalin insisted on continued resistance to the German invaders.

Axell, Albert. Stalin’s War: Through the Eyes of His Commanders. London, Arms and Armour Press. 1997, p. 168

Yeah sorry for infodumping on ya. just to let you know a lot of my comments have comments that include more reading material.