In The Communist Manifesto, what do Marx and Engels have to say about people in pain and who experiences pain under capitalism?

In The Communist Manifesto, Marx and Engels suggest that the way capitalism exploits labor for profit is painful for the working class.  
The Communist Manifesto is quite direct in attributing exploitation for profit as the reason that people suffer. Marx and Engels argue that capitalism is predicated on manipulation.  The wealthiest of people generate their profit at the cost of workers.  For example, the owner of the factory is able to make more money when the worker is paid less for their efforts.  The less the worker receives, the more profit the owner makes.  Marx and Engels believe this helps to explain why capitalism is synonymous with suffering and pain for the working class:  "These labourers, who must sell themselves piecemeal, are a commodity, like every other article of commerce, and are consequently exposed to all the vicissitudes of competition, to all the fluctuations of the market."  Marx and Engels feel the wealthy have no qualms about increasing the suffering of the working class in order to meet the demands of the marketplace.
Marx and Engels are emphatic in suggesting that capitalism's success is dependent on the workers' pain. Suffering is unavoidable.  Marx and Engels describe how "masses of labourers, crowded into the factory, are organized like soldiers" and exist "under the command of a perfect hierarchy of officers and sergeants."  Such control makes workers "slaves of the bourgeois class, and of the bourgeois State."  In order for capitalism to thrive, Marx and Engels believe that the laborer is "daily and hourly enslaved by the machine, by the overlooker, and, above all, by the individual bourgeois manufacturer himself."  Suffering is inevitable when capitalism reduces workers to slaves.  When the drive for economic profit makes workers a mere "commodity," the end result is the workers' pain.  As a result of its objectification of the working class, Marx and Engels blame capitalism for the suffering it causes.