In short its a curse on humanity and liberty. And to explain its a system which renders human rights, liberty and land owners worthless and useless. Communism is infact not a bad idea, in theory its one of the best system, but it fails badly when it is applied and practiced.
Communism is a system which indirectly tries to bring back monarchy or dictatorship while pretending to boost equality and eradicate poverty. The fact is communism either fails a nation and gets it collapsed(Soviet Union) or it improves the production and enables mass production of low quality and worthless goods(China).
On the whole Communism is exactly the opposite of democracy, liberty and modern societies.