Debilities are not just their stat modifiers; they have effects in the fiction. If you take Confused, your ears are ringing and your vision is blurred, and debilities are harder to heal than HP loss. 

I think you're worrying over nothing, but if you're really worried, just use hordes of weak enemies rather than fewer tough enemies. Bloody Aegis cancels only one attack, whether a 1d6 Kobold spear or a 1d10+3 Dragon Turtle bite. Pretty soon he'll only use Aegis in a life-or-death situation -- and your goal as GM is not to kill them, anyway, so why would he ever need to use it?


Wait - if you haven't had your first session yet, how does he have Bloody Aegis, anyway? It's a level 2-5 move.

I'll just point out that Acting Under Fire's 7-9 result always comes with a downside ("worse outcome, hard bargain, or ugly choice"), and this move doesn't seem to have a downside at the 7-9 level, so I'd be worried about players abusing it.

Spending hold to deal harm-as-established doesn't seem too powerful in itself; players can deal harm without a roll whenever the fiction demands it.

What about making it a choose-N or a hold-N move?

Roll+Tech. On 10+, choose 3. On 7-9 choose 1.
* You erase a specific piece of data from the system.
* You link a new access point to the system.
* You obtain useful information from the system.
* You temporarily crash the system.
* You make the system act randomly, unreliably, or dangerously.
* You don't leave any traces behind.

The choose-3 lets you do interesting combinations - e.g. erase your buddy's criminal record, leave a backdoor for later use, and make the system act wackily so they hopefully think it was just random vandalism.

It's not the stats, but the move that's chosen by context. Start with the fiction, compare it to the "when" part of each of the move descriptions. The best match is the right move to use.

Example 1:  You've been waiting for this for weeks. You've worked your way into NPC gang leader Brock's inner circle; he trusts you and has no idea that was your sister he killed all those years ago. He's bent over his workbench, back to you, cleaning his rifle. You pull your revolver, put it to the back of his head, and pull the trigger. Bang. 2-harm, ap, no roll needed.

Example 2: You're scared shitless of Brock, this was a terrible plan, you don't know what he knows, your heart is pounding, but he's got his back to you and it's now or never. With shaking hands you draw the revolver. Roll Acting Under Fire to get the shot off before he realizes what you're doing.

For a sniper move that uses Sharp instead of Cool or Hard, I think the way to do that by the book is Read A Sitch to find the right spot to lay your ambush ("best way in"), and act on that to gain +1 to the Seize By Force. Or be a Driver with Good In The Clinch and then Act Under Fire with Sharp.