It seems like this English sentence is missing something. Although it's not correct, how about "You have nothing to threaten me with"? or "You have nothing with which to threaten me"?

A better constructed English translation would be "you have nothing with which to threaten me. The translation supplied is incomplete.

"You have nothing to threaten me" is not English. You can threaten someone or something (like a career or future) directly: "Don't threaten me!" But when you threaten someone with something, there must be a preposition. "You have nothing to threaten me with/about/over." ("You have nothing with/about/over which to threaten me.") You could also say, "You have nothing that threatens me."

"You can't threaten me" would be a more normal English sentence.

I agree with these comments that "with" is needed here, but one of the hints was "endanger", which I thought would possibly work without a preposition: "you have nothing to endanger me". It wasn't accepted, of course!

"You haven't anything to threaten me with" is wrong?? Something is happening in this last part of the course where many feasible options are being ignored.

This is also true with other sentences but I have very hard time on hearing two M sounds. Seems like "pru-mu-na-se" for me. How can I hear the two M sounds (and one N sound)?