Main crime for Fisk: Racketeering (http://www.investopedia.com/terms/r/racketeering.asp )

Basically Fisk has extorted money (got money from people by threats, violence etc) bribed people and committed money laundering ie made illegal money look legitimate. He's also organised murders and such which would make him an accomplice to the crimes but I can't remember if I heard him charged with that. I definitely know he was charged with racketeering; I heard it in the scene when he was arrested.