My Krav experience is from the eighties, and it is not my primary style by any means (PDK is), but I am also someone who has been in a great number of altercations in my life, and experience has taught me that anything goes. It is not just a saying.
When my jaw was broken by a joe six pack I was too young and cocky to take seriously, i ended up with two screws in my jaw for the rest of my life, a $14,000 hospital bill, and six weeks out of work that led to my losing one of the best jobs I'd ever had.
Over twenty years later that nerve is still severed, I can only feel half of my face when I kiss my wife good night, and should I ever have future medical problems because of it, they will be pre-existing and not covered.
I was a black belt(had nearly 12 years in at that point and had done a lot of street fighting), the kid was an idiot...one of many in a long life of fighitng, cooking. bouncing.
Any attack- armed or unarmed can kill you, the attacker's intent has absolutely nothing to do with what effect they might have on you.
A broken hand can mean weeks out of work, a broken leg the same, etc... and a sad reality is that most who will attack you really don't mean you grievous harm, it is simply at the moment that more often than not they don't care.
Put them down, take them out...the faster the better.
Don't call the police unless you must, walk away. Wake up the next day go to work, train, live and love. Whatever happens to an attacker is more than deserved. Personaly at this point in my life I have learned to not even see them as humans.
I may sound sick to some. But I am going to work in the morning, I will wake up next to a loving wife, and I will train and work with others of similar opinion who are not stupid enough to die or be seriously harmed to hold up some societally accept concept of right and wrong.
I wish you the same.