You are at max allowed to respond to the aggression with the SAME AMOUNT OR LESS aggression as it was done against you.
Bullshit. If someone is trying to physically harm me I can do whatever I have to to make him stop. If a 300lb man is throwing punches at me I'm not going to try to punch him back, that would be worthless, I'm going to try to make him incapable of throwing more punches as quickly and efficiently as possible.
Doing equal damage as has been done to you is vengeance and biblical eye for an eye bullshit. Rendering them incapable of doing more damage is defense.
I don't give a damn to bible(just to let you know), its a matter of Libertarian philosophy.
Secondly if someone is trying to physically harm you, say beat the crap out of you, and you shoot him dead out of nowhere, that might be an aggression, but you show a gun to him and he continues and if you demonstrate reasonable that the guy never stopped initiating aggression and it became necessary to shoot him then no court will hold you responsible for the murder.
Stop acting like one of those Texans who shot a bunch of thugs who were running away from his neighbor's property. It may suit well for today's society, but its not fit for Libertarianism.
The main point is there are no hard and fast rules for this. If someone steps on your shoe intentionally there is NO WAY you will get to shoot him dead in a Libertarian society.
Just tell me this Ecolitan, do you believe in the fact that if aggression is made against you, it does not give you a right to "initiate"(not respond, but initiate) aggression against the other person??
If your accountant runs away with your money, and you go to his house and rape his wife, have you merely "responded" to the aggression or "initiated" the aggression??