You have to understand the nature of the beast before you can judge him.

Stalin was born into a fierce and angry household, his father beat him and his mother terribly... so bad in fact that one of stalin's arms was shorter than the other and next to useless, the beatings went on and on, and Stalin's father was a blantant alcoholic, one day Stalin had enough of his Dad beating him and his mom, and the only reasonable way to destroy that bond was to destroy his father... he killed him. At this time, Russian Authorities would have done nothing to prevent the ceasless assaults. After his Father's Death his mother sent him an Orthodox School so he could become a priest, he got in with a group of people who were Marxists, when the priests found out, he was locked into the School's basement for days, suffering from Hunger and beatings... instead of doing what the priests desired (I.E. Turn him away from Communism) it fueled his hatred for Religion and he became a full on Communist, and with good reason in my opinion, this is a guy who would not go down without right killing him.
Soon after, he left School, and joined the Bolshevik Party... at this time a band of guys who disliked the Czar because of the misery the Peasant Class went through (Stalin blamed the Czar for his terrible childhood), he became a petty thug and was arrested and sent to Prison several times, escaped Siberia 7 times! and then he finally gave up after the 8th, waiting for the Bolsheviks to take power. During his misadventures with Crime, you can well imagine he gained some pretty rough friends. During the Russian Civil War, Stalin was relieved from Siberia and given a position of power under Lenin (he commanded the Assault on Baku, and actually did relatively well for never having commanded anyone in his life.) After the Bolsheviks took power, Stalin got as close to Lenin as possible, and although Lenin didn't trust him, took him under his wing, as well as Trotsky. Trotsky and Stalin hated each other from the beginning, Stalin was a hard core Communist... coming from a land that historically hated the Czars (Georgia).
After Lenin's death, Stalin quickly took charge during the political vacuum that followed. He had pictures made, making him look as though he was close to Lenin, even though they were all superimposed, the people thought Stalin would be the next Lenin, they thought Trotsky was far to Liberal and Soft on many political issues whereas Stalin, who made himself look like a Leninist, would be firm. After Stalin took power, he deposed of any Political Rivals via the NKVD, many of which were Officers in his army.
His 5 year Plans were made because Stalin was aware that the Czars really cared more about personal wealth, then that of their people, he knew that these people would not willingly abandon their homes and jobs to work in some god aweful land building factories, so he forced them too, and with it got a taste of revenge. He never liked Cossacks who had invaded Georgia... so he deposed of most of them... he never liked Russians who occupied his Homeland, so he deposed of as many of them as possible... he was taught to hate these people as a Child.
Later on, his 5 year plans indeed proved more fruitful than even he expected even with Barbarossa. Had Hitler been kinder to the Russian people, most would've joined him, instead he took a hard line, the Russian People had a choice... Support the German Dictator or Support the Russian One? Obviously they supported the Russian One. Stalin was the first man to rule Russia in a long time to actually stir Russian Pride and Faith in the Soviet Model, even more so than Lenin.
Stalin gained many vices throughout his life, paranoia being the largest of them. Before he died, it was assumed he had writs of execution on 4000 people every day for 3 years, he had fallen into madness in his last years of life, and from years of stress and cigar smoking died in Rightful Agony. During his burial, the Russian people actually encased him in Concrete and dropped him in the ocean, such was their fear of him.

Yes, Stalin was a Diehard Communist in every way, shape, and form... he was a Communist with a taste for vengeance. His life story is very sad... and if you read a more detailed book on him, you'll understand him far more than what I have written.