Question

What was Stalin's main achievement?
What was he known for the most?

Answer 1

Probably the forced, rapid industrialization of the Soviet Union. During his rule as Premier, he instituted a number of directives and public works projects that literally lifted the relatively crude infrastructure (in comparison to that of Europe or the United States) into the modern age. This also enabled him to successfully fight off the Germans in WW2. The dark side of this is that millions died in purges and forced labor to help make it happen.

But he's probably more famously known for leading the Soviet Union through WW2 and eventual victory over Hitler's invasion on the Eastern Front. Though he almost considered surrendering, he decided instead to fight. He was a brutal leader who drove his people (many times, forcibly) into fighting the Great Patriotic War, but he was also canny enough to let his generals do the real fighting. If his generals had a good plan, all it really took was Stalin's stamp of approval to get what they needed regardless of the cost.