What did Karl Marx say competition and profit will do?

According to Karl Marx capitalists paid their workers just enough to keep them alive and working. The difference between the wages paid to create products and the price the capitalists received from the sale of these products would create the wealth of the capitalists.

A society's government would be controlled by the capitalists and not do anything to improve the lot of the working classes. If there were labor unions pledged to increase the wages of the workers they would be controlled by the government. Labor union strikes would either be outlawed or crushed by the capitalist government.