Oh, and they only had to kill millions of people to do it. Stalin admitted to Churchill that his purges killed more Russians than Operation Barbarossa.
Right, right, Stalin strangled thirty million babies with his bare hands. We get it. I'm not defending the purge. But in no way was it a necessary part of Russia's modernization - this is the equivalent of saying that the U.S. created the Nuclear bomb, but had to intern 120,000 Japanese citizens to do it. It was the same regime and the reasons were not totally unrelated, but it's clearly not a cause-and-effect relationship. Not that anything you've actually said has even argued with the idea that the Soviet Union was, if nothing else, pretty economically powerful.
Additionally, Britain managed to go from agriculture to an industrial power in a similar amount of time, and guess what? No purges or genocides.
Right, not of it's own, but let's not pretend that British industrialization wasn't based on horrific imperialism. Not that it's particularly relevant, because you're comparing the time it took for countries to industrialize, while I was comparing the amount of time it took for countries to modernize, where the USSR blows Britain out of the water (which is not exactly a fair comparison either, but again, all I want to say is that if the idea that the Soviets were an "economic failure" were true they wouldn't have been a super power that rivaled the United States for 45 years.
And finally, how's the Soviet Union's economy doing now? Oh wait, it hasn't existed for 20 years because of their creaky, state-run economy.
Right, state-capitalism is a model that's inherently incapable of producing a strong economy. That's why China isn't an economic super-power.