I think having to sustain an injury first in order to have a justified lethal response to an imminent threat is an unreasonable standard. The threat has to just be real. People don't have a right to injure you, but of course escalation of the use of force has priority levels--force meets equal force.
My security guard friend has suggested adding mace to my everyday carry for the "in-between" situations--like many others in this thread--but warns that wind direction, capsaicin tolerance and other factors can confound its use. He carries a tazer for 'in-betweens' and says that I should look into getting one as a superior alternative to mace, though I think only LEOs and security companies can get them. Important note: a tazer is different than a flea market stun gun. My friend who is a survivor of domestic violence attests that mace won't stop someone dedicated to fucking you up--it'll just piss them off more.
Example: guy with a weapon/big motherfucker/multiple aggressors hasn't hit me yet but it's obvious it's incoming and I can't escape, my belongings are not sufficient prize, I warn him I'm armed and not to advance, I back up, he advances anyway, I pull and shoot before being bludgeoned/stabbed/broken. This would be the "going on the offense" I referred to in the quoted text above. If they don't pull a weapon and tell me to strip or something obvious I don't have a rational motive to comply with so you have to assume the worst before you're unable to do anything at all. It's surprisingly easy to get beaten to the point of disability or death.
Not an example: Anything I can talk down, walk away or run away from. A pissed off guy wants to throw a few punches and shoves and get on his merry way--I happen to be in that way. Customer service, bars, ratchet house parties--it's happened before, it'll happen again. Not a life or death situation, the aggression is general, not specific, and the body language doesn't indicate premeditated focus that comes when someone is out to get you, it's chaotic, disorganized, and mostly aimed elsewhere. Crazy hobos fit in this category more often than not. It's a pretty specific set of scenarios; I don't plan on using this thing often.
To take this back to its source: in the scenario I encountered, I would have had to have been attacked right as I was entering my vehicle--before I could get my door closed--to make me seriously consider using my weapon. The accomplice could then join in easily. Mace would probably backfire. If I ran, instead of attempting to enter, I had nowhere to go to--nowhere was open except maybe the nearby strip club--and I lost visual on her friend (also my knee is not that great). It was that thought specifically that made me realize my options could be extremely limited within that timeframe and I was all alone. Wasn't much margin of error on my end to get away unscathed.
I can see an interpretation of what I wrote above as "I would just shoot anyone I thought would hurt me [vague] and in some magic fairy land people who get shot don't die" in the way I worded that, and I thank you for being specific, giving me a quote and a problem--it gives me something I can actually respond to instead of the nebulous and general "lol psycho killer small penor gun nut stop being poor and let urself get beaten up," posts in here. I think I got what you meant. To elaborate on the other half of that: I would prefer to make it to my grave without hurting anyone. Ideally anyone I would have to draw on would just fuck off without a trigger pull as soon as they see the thing, so I'd sleep better at night and he could reconsider his life choices, but I'm not going to draw it unless a trigger pull would be warranted (I am about to be rendered completely helpless, get fucked up, or die). One of those "I would be in the right, but no matter what I wouldn't feel right about it because it's another human being" type things. It's not a realistic expectation, just one I am 110% happy to accept if it comes about--these things do happen sometimes. If I do pull I expect to have to empty an entire magazine into the person trying to kill me to get them to stop, which will result in their death.
I don't want to run out of options should the worst happen. The most realistic expectation is that this hunk of plastic and metal rides in my crotch for decades doing little outside the range but weighing down my belt and collecting lint for me to clean out periodically--one of the reasons I went with a single stack chambered in 9mm.