Haven't you seen any mafia movies? You can't just go after the mob like that. They'll cut up your family and feed them to the fishes. But the MC may figure out a way to get the mafia off his back. Stay tuned!
those are movies, in real life they just whack you and drop you in a hole somewhere lonely, or feed your body parts into an incinerator, or drop your body in a steel blast furnace.
truthfully they really don't care for cutting ppl up, too messy, too much evidence. now let's say you were a member and had taken the oath then snitched to teh cops, before they kill you, they'll kill your family, your pets, burn down your house, car anything you own and everyone you love, then they'll kill you, that's called destroying your world. and yes they do still do that which is why you rarely hear about mafia ppl telling on the others unless they have nothing and no one.
there is one way to go after the mafia, make it costly, they don't like that at all and will often stop everything and leave it be for a while hoping you'll calm down and forget. once you do tho it becomes open season again haha
but the biggest method is to find who ordered the trouble on you, take them out and the others will drop it cuz it wasn't their doing. beware tho, if the one who ordered it is a real family member, you'll need to remove his entire family.
remember the most important thing to the mafia is business, as long as nothing interferes with that business, they're happy, interfere and they remove the problem.