Galina "Red" Reznikov
It's not completely clear what exactly lands Red in prison, but we do know that she and her husband owned a restaurant and that Red became involved with the Russian mafia. She punched one of the mob wives in the boob and ruptured an implant, but her solid business advice to the husband allowed her to stick around.
In season four, we find out that Red had several heads in her freezer at the time of her arrest.