Ceres
This is the abandoned first attempt, brought to you by the founders of Oberon. A large group of Elites formed a colony here after the great Ganymede war. They opened with a aim towards the night life: casinos, clubs, bars, things to bring in easy cash flow with definite returning customers. Things were going well for a while, until a few too many rivals opened up on main street and people weren't making the money they anticipated. Secretive hits started taking place, then public ones, then bombings, and things kept getting worse. This elite had been keeping Monmatia PD out, Hunters payed off, and could now feel CIBI breathing down their neck.
After some hedge trimming, the amount of rival businesses came to a balance and things were peaceful for a little. However civilian casualties and system wide controversy was more than enough for CIBI to start invading and ending the goings on of the Elite.
After several attempts the crime was never completely flushed out and they kept multiplying underground. Funding was pulled from investigating Ceres and it was claimed as a lost cause like Venus and Rhea.
About 20 years later, the underground crime presence surpassed any regular old local blue collar worker population that existed, and the underground became all that there was. There is a 0% chance any work on Ceres is at all connected to a gang or violent organization. The chairs on Io decided it had gone so far they discussed eradication many time but the votes never clear and it somehow stays safe from interstellar interference as many organizations based here have EXTREMELY lucrative assets across the system that would do everything in their power to keep the benefits safe.