Reluctant Kiler variations: pulled punches, fright checks.

[Bruno]

Reluctant killer gives you penalties to hit "people". There's at least another two other ways that deep discomfort with actually hurting people can manifest: not being able to use your strength, or having to roll a fright check before you try (if you manage to make yourself try).

Pacifism: Totally floppy punches [-10*] (needs a way better name, not sure on the price.
So, personal anecdote time. I can't strike into a human-shaped target, ie I can't aim beyond the surface. That means I basically only ever deliver light taps, slap, and shoves, unless I screw up.
Even if they're wearing a face-obscuring saftey mask, and even that one time when I jumped them from behind and was volcanically angry (not proud of that incident, but I was 12 so yeah).
I can't even break a board if there's someone holding it; you brace the board out in front of you, and from my POV your face is on top of the board and *baf baf baf* I can't break it. My teacher clued in and offered me a chance to try in the rather less well braced position of one person holding the on either side. I was warned this is harder to break because of weak bracing, but I seized the opportunity, and I did it first try. The damn board wasn't "people" any more, it gets a foot through it.
It feels like I'm stuck with a -2 per-die damage penalty on melee attacks (don't know if that counts on thrown objects, my throwing sucks so I've never tried).
For usefulness in RPG adventure gaming, let's say it has a self-control rating, and you get a bonus under "Justifiable" circumstances (basically, the more it sounds like someone with Pacifism (Self-Defense Only) could do it, the more likely you can do it.

I probably have an abysmal self control-rating, but I'm not an adventurer and I'm fortunate live in a peaceful environment :thumbsup:

Phobia: Being violent [?*]
The other one is probably basically a phobia of being violent, and can be treated as such. I don't know if you have to make a fright check per fight or per target or per individual attack. Probably all three are valid, with different point costs.
Dramatically, there's the narrative of the conscripted soldier sent out to a real battlefield finally, and having a meltdown over having to actually shoot people. You get the best storytelling for this when the soldier is a sniper or other protected specialist, and thus has the luxury of sitting around not being murdered while they have hysterics, but I'm willing to bet This Is A Thing IRL.
In your standard narrative, they get over it when an ally is wounded or killed due to their inaction, and trade it in for Callous, Fanaticism, Intolerance (the enemy), and suchlike. Then a romantic interest helps them recover emotionally, cue happy ending. In a more realistic narrative, I'm betting some of these people don't get to quickly ditch it, they make a crap ton of fright checks, and collect disadvantage points like they're going out of style before the GM lets them trade the disad in, and their complimentary pile of fright-check induced disads is PTSD.

This isn't Post-Combat Shakes, because that lets you get into combat just fine, you only have your freak-out afterwards.