Yeah, you do have a self-help option...
SUE THEM! It elegantly solves all the problems
Because of the fraud, they're into you for at least triple damages, and possibly a lot more if their behavior would enrage a jury.
Suing someone is a "self-help" legal solution that allows you to forbid, compel, or take money damages. You can't send them to jail, but if their conduct is illegal and disturbing, the judge can refer the case to the District Attorney's office for criminal prosecution.
In this case you engage an attorney.
- This can be out-of-pocket in which case you pay the lawyer regardless, but keep all money collected.
- Or it can be on contingency, which costs you nothing out of pocket and you get 2/3 - (the lawyer collects 1/3 for services rendered) -- but a lawyer will only agree to that if a) your case is winnable and b) the defendant is collectible.
- Lastly, you can self-represent if you really, really want to... but unless you're careful, detail-oriented and willing to do a lot of research, you'll probably find yourself swamped with technicalities.
Now, what about those downsides?
"They are criminals and they beat you up or murder you":
They won't get to meet you. Their first encounter will be with your lawyer's process server throwing a piece of paper at them. If they threaten or intimidate the process server, those will a) be completely new crimes, which the process server (as an independent third party) will gleefully report; and b) this will wildly prejudice the lawsuit in your favor.
Other than that, they interact with your lawyer and the court.
If they're an organized crime ring, they'll have their own lawyers, who will use the legal system to resist you. Not their first rodeo; they know better than to physically threaten lawyers, process servers, or litigants.
"They are innocent victims, tricked by the real scammer to be a money mule":
They'll have every opportunity to raise that objection and explain their side of the story. They don't even need to hire a lawyer; they can either write it in a proper Answer, or they can explain in interrogatories (written Q&A you send them), or they can tell you the story in front of a camera when you take their deposition.