"Suckering Someone: When you attack someone unsuspecting or helpless, ask the MC if you could miss. If you could, treat it as going aggro, bur your victim has no choice to cave and do what you want. If you couldn't, you simply inflict harm as established." If you can miss, you roll, but on 10+ they have to take the harm - they can't cave. To quote, "Since the victim doesn't have the option to cave, a 10+ means they have to take the harm." If you can't possibly miss, there's no uncertainty to roll for, so they take the dmg. I think I described it fairly as being the replacement for Go Aggro in certain situations. Perhaps I should have used more nuance?
As to GA:
"If that's not the Move for threatening violence, what is it? How could it be more clear?"
Because "to do it, do it." Going aggro is triggered by going aggro. Going aggro is given a definition on pg 139: "Going aggro on someone means threatening or attacking them when it’s not, or not yet, a fight. Use it whenever the character’s definitely the aggressor: when the target isn’t expecting the attack, isn’t prepared to fight back, doesn’t want to fight back, or can’t fight back effectively." Which, broken out, goes back to the numbered list I provided in my previous post. In other words, a shit-ton of things unrelated to threatening someone seems to trigger the "threaten" move. To quote, "Going aggro on someone means threatening or attacking when when it's not, or not yet, a fight." It's literally inclusive of "shooting someone in the face who thought we were still having an argument", which involves no threats, and no caves to in (that actually seems to turn it back into sucker someone). In fact, the 7-9 description suggests you *didn't* threaten: you actively attacked ("A 7-9 is a hit, but that doesn't mean the attack itself has to connect") as your means of altering behavior.
Meanwhile, "threats" are explicitly listed under Manipulate.
It used to be clear that Go Aggro was "earnest threat of violence, where failure to get what you want *would* end in violence" and manipulate was "empty threat of violence." Now Manipulate really doesn't give a shit about whether your leverage is sincere or not, and Go Aggro is expanded to "attacking someone who's not expecting to be attacked," with conflicting examples as to whether a threat is actually involved. It's actually not at all "the" threat move; it seems to be "the" "uncontested violence" move, with "threat" being "verbal violence", but... no. No, it's definitely not so clearcut "*the* move for threatening violence" that it couldn't be more clear.