Contrary to what you seem to believe (maybe because some European governments seemed to say it was "not proportional" because there were 9 killed on one side and 0 on the other) proportionality is not related with any kind of ratio (well...not in law at least)
For example, if there is a huge threat and that the only way to avoid a danger is to take extreme measures (such as slaughtering millions of animals during the "mad cow" or the swine flu crisises) it is "proportional".
It was proportional to kill and cremate millions of chickens to avoid further contamination and possible human deaths.
Proportionality is not a ratio, it is (roughly) the 3 criters I have mentioned. You can trust me, I have studied that in Constitutional Law 3 years ago (if you can search in the archives you should be able to find a very old thread where I was already saying the same)