Marx and engels saw capitalism as an inherently exploitative economic system that disproportionately rewards the rich while failing to reward the poor.
Because the rich were also those in possession of political power, Marx and Engels rejected the idea that social or economic change could be brought about without overthrowing the existing system.
in their book 'The Communist Manifesto' they stated:
"workers of the world unite: you have nothing to lose but your chains"
they argued that capitalism would inevitably lead to a violent revolution.
Luxemburg believed that a form of revolution was necessary. She criticised the "violence of the ruling class" - the economic exploitation of the proletariat by the bourgeoisie.
She argued capitalism could be defeated without resorting to violence and democracy could help achieve socialism.