Chimp with a Machine Gun
It is a deliberately ugly line. Chuck uses it to dehumanise Jimmy and to justify the lengths he is willing to go to keep him out of the law. The metaphor is partly fair: Jimmy genuinely does take risks, bend rules, cut corners, and put real people at real risk. It is also partly unfair: it leaves out everything human about Jimmy, and treats *capable of doing damage* as the same thing as *guaranteed to do damage*. That tension is the whole point of the show.