Dekulakization was the process of collectivizing agriculture. This process was frustrated by Kulaks, bourgeois plantation owners, killing crops and their farm animals, rather than handing them over to the red army, and even getting into skirmishes with the red army. This led to famine. The reasoning for collectivization was absolutely driven by Marxist analysis, so we can file this under "deaths that happened because the Soviets were trying to bring about Socialism," though the blame is absolutely on the Kulaks.

The 1930s famine was a tragedy, accelerated by drought, though the Ukrainian Communists hid how bad the famine was getting until it was too late. This can be considered partially state responsible, though obviously most of the blame is on the Ukrainian Communists for trying to hide how bad it was getting. It was more of a human error compounding a natural famine, hard to attribute it to Marxism or not.

Those that died during the purges? Yep, the fascists, White Army war criminals, rapists, anti-semites, and murderers made up the majority of those executions, and these people may have lived had the Tsar remained. There likely were innocents killed as a part of the chaos, though. All in all, definitely a consequence of the Socialist system defending itself from an onslaught of infiltrators.

Deportation? Not really driven by Marxism, and I don't know enough about that particular subject to speak on it.

The USSR as a whole was formed based on Marxist analysis, it was a largely publicly owned and centrally planned economy. Life expectancy doubled, literacy rates over tripled to 99.9%, healthcare, education, and childcare were free and high quality, and working hours were lowered gradually and vacation days were higher than in the US. Whether or not the USSR was following Marxism isn't in question, it absolutely was for the bulk of its existence guided by Marxist analysis, even if errors were made along the way.

On the other hand, Capitalism kills millions directly every year. The US Empire committed many deliberate genocides during the USSR's existence, while the Soviets stopped the Holocaust. You are happily accepting the US State Department line, and doing their work for free.