In the criminal underworld when a man becomes so powerful he is able to show up at another man's home and kill him without repercussions, there are two people involved in this scenario. The one who opens the door and gets shot, and the one who knocks.
I am not in danger, Skyler. I am the danger. A guy opens his door and gets shot and you think that of me? No. I am the one who knocks!
Describes the person who is doing, working, acting. The term is used as a way of telling the bearer of unwanted, unnessesary and bullshit advice to shut up, fuck off and leave you alone. Its a way of letting them know that you are the man and yuu have the current situation under control. Or can also describe the more dominant person as in the guy who tells other the way its going to be.
My boss was a fucking legend but I thought he was doing something wrong. So i tried to offer my advice and he responded with "I'm the one who's fucking the chicken". Or my girlfriend being a pain in the arse and doing shit that is pissing me off so I had to tell her listen bitch "I'm the one who's fucking the chicken".