Here's an extended example that's popped to mind, and I'm just trying to see if I've got the Moves right: a fighter launches himself at a cave troll. He attempts to leap onto its back, defying danger--and fails. Instead of scrambling onto the monster's back, he finds himself plucked out of the air and slammed up against the cave wall and pinned there (Turn their move back on them).
I would consider that more of "Put them in a spot" but I guess "Turn their move back on them" works too. If that's what you're going to do, that doesn't deal damage. Remember, you choose as hard of a move as you'd like, but only one move. So:
"You're slammed up against the cave wall and pinned there. The troll is holding you down. What do you do?"
You let the player have a chance to save himself from damage, if he'd like, probably through another Defy Danger roll. Deal Damage is a distinct move which you could have used but chose not to. An example using "Deal Damage" instead of pinning him down:
"The troll grabs you off his back and slams you against the wall of the cave. Take d10 damage."
Simple, right? The fiction is mostly the same, but the effect is dealing damage instead of putting him a spot.
Could the impact also (or should it be only?) stun him? In reaction, the fighter wants to fight his way free (his allies being too preoccupied to help.) Would this be a fair distinction: a -1 to hack and slash as his broadsword is awkward at this range as he tries to pommel smash the troll's wrist?
Or would this be a case of defying danger to break free, rather than hack and slash; if he'd attacked the troll instead, looking to hurt it rather than get free, then that would be hack and slash? Can he combine the two, hack-and-slashing the arm to get he troll to drop him, but also inflicting harm? Or should a Defy Danger get mixed in there?
I usually only see stun or debilities happen when you deal damage, since stun is a type of damage. I don't think there's anything that specifically forbids using debilities without dealing damage, but my group usually just does debilities when dealing damage. As for the -1 to Hack and Slash, I would think that a better solution is what you set out later: Defy Danger to break the pin, then Hack and Slash.
My big question is: can he really deal his full die of damage pinned down like that? He would, if he succeeded with the -1 penalty, and pummeling a troll with a pommel doesn't seem right for that. If the fiction doesn't let him, then you shouldn't let him roll. Instead, say:
"You can't bring your sword to bear while you're pinned. What do you do to break out of the pin?"
A little leading question, I grant, but you have to make sure the players are making moves that follow from the fiction, too. I think Vincent has written somewhere about how he used to have penalties and bonuses built in based on how hard things were to do, but he nixed them because they didn't add anything narratively to the game. Either you can do it--then you roll it--or you can't--then you don't.
Say the poor guy fails again; now the troll pitches him across the room (separate them!), where he smashes into the opposite wall: damage that skips armour? Or rather: he dents his sword against the troll's hide (use up their resources)--would that give it a -1 until he hammers it back into shape or finds a replacement?
One, I don't think "across the room" is really separated. And again, one move on your side, not two or more. It can be a harder move than "Separate Them" though. This is a troll and he's not messing around! Deal some damage, already. As for Ignores Armor, that makes zero sense to me. His armor would definitely protect him from a blunt trauma, even if nothing else. So, some options:
"When you're trying to ________, the troll flings you again into the opposite wall (stunning you?). Take d10 damage. What do you do?"
"You make a huge swing of your sword at the troll and manage to hit him in the crack between his armor plates. Great news! Until...he shifts a bit and your sword CRACKS OFF AT THE HILT. What do you do?"
If you're going to "Use Up Their Resources" don't pussyfoot around. He can repair the sword if he defeats the troll and grabs the other half stuck in the armor, and reforges it. For now, though, a -1 ongoing isn't interesting, it's just annoying. Actually take his sword away from him: he failed a roll and you're trying to fill his life with adventure. Big adventure to try to stop a troll with only a hilt! Or maybe he goes in for the blade and wields it anyway. Who knows what he'll do?
tl;dr: use one move. The move should follow from the fiction: blur the lines a bit between circumstance and mechanics. As Apocalypse World says, "misdirect". Although you might just be dealing damage, you can set up his positioning such that the battle feels dynamic. Don't pull your punches. But you only get one move, as hard and direct as you like, and then you let the players have their turn in the conversation.