Money
Like all tools, mass cooperation through money is a double edged sword. It's behind every war, every genocide, every enslavement. It's also behind every medical treatment, every piece of food in the grocery store, every act of emergency aid.
Without money, yes, we wouldn't have large scale devastation and consciously inflicted suffering. But we would also all still be living in huts and caves regularly dying of dysentery and starvation and would be lucky to see 2-3 of our 12 children make it to adulthood.
There are examples of war and enslavement that pre-date minted currency. Non-barter forms of exchange probably allowed for a specialist warrior class to develop though.