Why so many corpses?

In our bourgeois democratic societies we have a number of protections against the power of the state. We can form political groups to forward an agenda which makes changes we think are desirable. We have the right to express our opinions and seek redress in law.

The Manifesto would deny these rights.

By this, the long-wished for opportunity was offered to "True" Socialism of confronting the political movement with the socialistic demands, of hurling the traditional anathemas against liberalism, against representative government, against bourgeois competition, bourgeois freedom of the press, bourgeois legislation, bourgeois liberty and equality, and of preaching to the masses that they had nothing to gain, and everything to lose, by this bourgeois movement.

The above would destroy the protections that we have against the arbitrary power of the state. These protections disappeared in the Marxist states, and nothing replaced them.

The Manifesto cited an enemy which would be defined at the pleasure of the state and party, specified an all-powerful state and removed all protections of the individual from state oppression. The Manifesto also specifies what should be done to these individuals:

You must, therefore, confess that by "individual" you mean no other person than the bourgeois, than the middle-class owner of property. This person must, indeed, be swept out of the way, and made impossible.

The corpses were a product of the recommendations of Marx and Engels. The Communist Manifesto is a manifesto for mass murder. Torture, gulags and the bullet in the head are all ways of sweeping people away and making them impossible.