Complex sentence: Slowly but surely using his disguise as Marco Xavier the Martian Manhunter worked his way up through the cartel, while maintaining the original Marco's role as an outside contractor uninterested in joining Vulture, he is eventually able to smash the group from the inside.
Split into simpler sentences: Slowly but surely and using his disguise as Marco Xavier, the Martian Manhunter works his way up through the cartel. While maintaining the original Marco's role as an outside contractor uninterested in joining Vulture, he is eventually able to smash the group from the inside.