If you exclude the outliers like Campuchia and Nazi Germany, even the most benign commies are always way more deadly than the most ferocious fascists.
Unification was supported by both sides among the people, most South Koreans supported communism and 70% of them supported unification with the North. South Koreans didn't even support their own government, they were dealing with internal insurrection from their own people. The North was an industrialized nation and the South was a poor farming country and their unification would of been hugely beneficial to both. The war would have been over in another 2 weeks without intervention and a minimal amount of casualties, and it had only been 3 months from the start of the invasion. The only people not in support of it at the time was the political leaders of SK at the time because it meant they personally as individuals would lose power and wealth, and the US who was on a crusade to crush and kill anybody who dared support communism. Korea never should have been split in the first place, but the US and USSR had to be little bitches and force their will upon these people.
Killing 5 million people, most of which were innocent civilians, in the name of "fighting communism" is evil, not the idea of a unified nation of people supported by those same people.
Soviet occupation. Korea was supposed to be unified and elect a government back in 1950, Soviets made sure it didn't happen because they had no chance of winning.
That and, you know, the whole invasion thing.
Pretty sure the soviets were perfectly fine with the North taking the South considering the South was US aligned which gave the US a foothold right on their doorstep. And again, the vast majority of Korean people on both sides supported Korean unification. The South Korean leadership, which was basically appointed by the US for their pro-US and anti-communism stance, was so unpopular among South Koreans that there was civilian insurrectionists trying to topple it. The South Korean military upon invasion couldn't even keep its own troops from deserting in significant numbers, and they even blew up a bridge full of refuges to try and stop the advance which it failed to do.
Yes the North invaded which is generally bad, but they did do it with popular sentiment among the people, and they weren't attacking and killing civilians along the way.
And regardless of all that, none of that justifies the US response of bombing and killing millions of civilians and leveling entire cities. The Korean War is considered the most deadly war in Asia ever, and had far higher percentage of civilian casualties than WWII and Vietnam.
I guess if I have to explain it I might as well not bother.
The entire analysis of capitalism which articulated the class system with which it replaced that of the pre-existing aristocracy and revealed the elimination of class to actually just be a switch in its structure and elevation of a new ruling class was by Communists.