Socialism

He is an ambiguous person. He certainly did a lot of good things, but there were mistakes and even from our point of view, quite cruel decisions. It is difficult to assess why he made certain decisions. There is a lot of unconfirmed information and ambiguous accusations around him, although, of course, there are bad decisions, maybe we don't know all the information, or maybe he was wrong. It was a difficult time back then. According to some reports, at the end of his life, even Lenin treated him ambiguously and was afraid of the concentration of power in one hand and even wrote a letter to the congress, but some doubt this, so it may not be true. To truly understand this, you need to be a historian and read a lot of original documents by yourself. But I don't think that we should consider him only a complete villain, as he is often exposed.

From my limited understanding Stalin tried to change things too fast. A comparison that would piss everyone off is like Elon Musk going all-in on robotics in an underdeveloped country.

In the long term Stalins policies paid off, but a lot of people starved because as it turns out putting all your points in technology means you don't have farms.

Gulagging bourgeoisie also isn't bad per se. But Stalin definitely sacraficed innocent people in the crossfire.

From what I understand, people who were sent to Gulag mostly were Nazis, bourgeoisie (basically people like the UnitedHealthcare CEO) and counter-revolutionaries.

I'm not saying it was the best way to seize resources from the rich and prevent counter-revolution. Some of the things he did were good, and some were bad.