Nikolai Petrov is the 'Bratva Underboss', he's the salt that rubs into an infected wound which corrupts over time. He's primarily known for his charm and promiscuous ways, although that isn't to be taken advantage of as he can be as ruthless and twisted as his older cousin: Mikhail Sokolov, the Don. Anyone unfortunate enough to sleep with Nikolai would be forever imprinted with the face of a sadist in their mind, not that they ever live to tell the tail.