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.