My theory for why the host always gets away with it

I think a question a lot of people have is what's to stop the "winner" of the game from contacting the police? Call the cops, tell them this psychopath forced you under a death threat to play this awful thing, and get your revenge. We know Iris is just interested in saving her brother, but what about other winners?

So my thought is the host ALWAYS gives one of the final two players a choice between killing the other player and getting the money, or sparing them and leaving with nothing. We see he did that with Iris, and I think for every game the guy has, he ends it like that. Because now, if the winner chooses to kill the other player, they just committed straight up murder. If Iris, or another winner, went to the cops, they could be charged with that last murder. And my guess is the host has that final murder recorded. So if anyone rats on him, he just has to show the recording of the winner being offered money to kill a person, or being able to leave freely, and the winner would go to prison to.

Now, the winner could still try and argue extreme emotional distress or or they did it out of fear, but it would be tough. Especially since I'm guessing host is good at cleaning up and covering his tracks, and the only evidence would the video he provides of the final murder.

As for how he'd convince someone who refused to kill and lost the money, thats another question. Maybe just threaten them. Maybe tell them his MI5 bodyguard would stalk them. But thats my theory for people who take the money. He always, always, makes them kill someone else willingly to end the game.