Every single one of the worst dictators of the last century was a socialist – Chairman Mao Zedong, Adolf Hitler, Josef Stalin, Kim Il Sung, Fidel Castro, Nicolas Ceausescu, Saddam Hussein, Muammer Gaddafi, Nicolas Maduro, Kim Jong Un, and Pol Pot. Do a search on any of them to read about their atrocities against their own people.
I think most of these dictators started with GOOD INTENTIONS. They genuinely thought that socialism’s promise of “sharing everything” would lead to the utopian society promised to them by Karl Marx. Once they came into power, they tried socialism. The fundamental problem with socialism though is that no one wants to work just to have it all taken from them and given to people who don’t work. So pretty soon NO ONE works. Then the leader who once had good intentions starts to FORCE people to work. And once you start to force people to work, you can never let go of power since those people will want vengeance. And that is how a dictatorship begins.
By and large, socialism tends to depend on the creation and maintenance of both internal and external enemies in a way liberal democracies generally do not.
You see it in how revolutionary and authoritarian socialist regimes lean on class struggle as their primary framing, since their ideology already casts society as workers locked in conflict with owners.
When socialist economies stumble, the state often points to saboteurs, counter revolutionaries, or foreign agents, which neatly shifts blame away from policy mistakes and onto convenient villains. That move helps justify more state power and fewer civil liberties, all to defend a revolution that usually needs defending only from its own choices.
There are some caveats or course. Its not hard too point out that this habit is not exclusive to socialist states, because governments of all kinds reach for the same playbook. That being said, democratic socialist countries are less likely to dip/fall into this pattern since the rule of law limits the government’s ability to hunt for enemies that are not there. As American political parties increasingly expand their powers on a rotating game of political Russian roulette, the ability for the system to stop this kind of fear mongering diminishes.
TL;DR-
Socialisms basic inclination to creating class division, and its propensity towards beginning with authoritarian structures after a revolution, results in a lot of the excesses in violence and suffering caused by socialist governments in reality.