No, he's clearly not a killer unless forced into it by circumstances (if it's either the guy agressing against me or me, I prefer it be the other guy). He deals justly, they broke bones and caused injuries which were returned to them with a spot of interest; I can't see anything wrong with that from a moral or valid philosophical point of view (I said valid, Dumbles' "redemption at any price" approach is not, to my mind, valid or moral).
Twill be most intersting to see how -this- Harry fares with more confidence and knowledge than canon!Harry.
Author's response
do not even trouble me with the name of that wretched sap canon!Harry. I will never pollute my story with any kind of weakling like that one.
Dumbledore may criticize Harry for his choices but Harry'll just brush him off with something like "if it's them or me, it's going to be them."
and Harry does indeed make just choices.