From the communist manifesto:

Freeman and slave, patrician and plebeian, lord and serf, guild-master and journeyman, in a word, oppressor and oppressed, stood in constant opposition to one another, carried on an uninterrupted, now hidden, now open fight, a fight that each time ended, either in a revolutionary reconstitution of society at large, or in the common ruin of the contending classes.

Does common ruin mean a miserable outcome where the oppressed classes 'lose' against their oppressors? Or is it a situation where all classes suffer? Or does it mean something else?