Complex sentence: These two social power factions were founded by the two thinkers Proudhon and Marx, the former being the social and secularist republican (anti-monarchist) individualist, and the latter the socialist anarchist (communism) collectivist.
Split into simpler sentences: These two social power factions being founded by the two thinkers Proudhon and Marx. Proudhon being the social and secularist republican (anti-monarchist) individualist and Marx the socialist anarchist (communism) collectivist.