I know you're probably exaggerating, but I think it's interesting to see from where Stalin came and what allowed him to thrive.
The USSR was never envisaged as a lone red state in a capitalist world. The impetus behind the October Revolution came from Lenin and Trotsky, who both believed that Russia could skip or "manage" its capitalist industrial transformation under workers' rule, while the rest of Europe had its socialist revolution after WW1. (Interestingly Stalin was one of the most cautious and inconspicuous leaders then, he felt that the Bolsheviks should have be more supportive of the (unpopular) Provisional Government and less radical socialist parties.)
Of course, Lenin/Trotsky's European dreams, inspired by Marx's theory, fell flat - after the German Social Democratic Party collaborated with right-wing militias to suppress the Spartacist revolt (Rosa Luxemburg), the prospect of left-wing revolution in the advanced capitalist countries was over.
Now, you had an isolated, agrarian, and fairly un-industrialised country, with the ruling revolutionary party having fallen out with all other socialist parties, with a civil war supported by all major world powers (Japan, Germany, France, UK and US all supported the Tsarist Whites against Trotsky's Bolshevik army). This was about as far removed from an internal revolution in the centre of capitalist power that Marx envisaged. Some of the measures (like re-forming the the secret police, Cheka) I can understand given how precarious the situation was. The reinstatement of small-scale capitalism to revive an economy torn apart by almost a decade of war (Lenin's NEP).
The problem is the scale of the power given to the Cheka, the fact that they were in totally uncharted territory and could see that the NEP wasn't going anywhere utopian fast, the fact that as a war measure they had effectively destroyed the power of the very Soviets (workers' councils) which had given the support and legitimacy in 1917. They were now cut off from the people, having promised a utopian future and coming nowhere near it, had reduced (once very lively) internal party debate, and were under no democratic control.
I think the particulars of what Stalin did were because of him, the purges were the result of his paranoia, the return to social conservatism: the recriminalisation of homosexuality, toughened divorce laws, and pro-family/motherhood propaganda, was definitely his personal choice, but the collectivisation and rapid industrialisation were actually Trotsky's policies that he appropriated. Maybe some ruling dispensations would have re-delegated actual power to the Soviets and peasants' councils after the war, maybe some would not have set insane work or food targets, maybe some would have given consideration for the workers on whose behalf they were ruling. But I can't imagine any such massive unprecedented transformation would have been "nice" under any ruler. Indeed, everywhere from Europe itself to the colonised 3rd world, the move away from feudalism has always been bloody in various degrees.