Canada

It's literally in the title: "Assault charges dropped against Ontario man who confronted [emphasis mine] home intruder"

My point of view is that the altercation became necessary the moment someone smashed windows and used the smashed window to gain entry into the house. You're forcing someone into making a split second decision at that point, and you can't expect those decisions to always be the correct one, and I don't think it is criminal to make what might be the wrong decision (or might be exactly the right decision) in such an extreme situation. In the even more extremely unlikely event that the intruder actually had a legitimate reason to be breaking windows and entering the house that way I would call it a very regrettable and unfortunate accident, and it is a very difficult stretch to imagine that actually happening in the real world. But accidents do happen, and they are unfortunate. I don't think that kind of accident would happen very often.

Otherwise I have to assume they are probably either going to try to get the fuck out as promptly as possible which I would strongly encourage them to do, or they are armed and are going to be starting an altercation themselves with me in the very immediate future which will likely result in my demise. And it's definitely self-defense at that point. I don't think it is reasonable to be waiting for proof of the need for self-defense to actually start, because by that point it's probably too late.