If you kill a man in your home in Ontario simply because he broke in and "presented a threat" you can expect to serve a murder sentence. Everyone from my gun instructors to police, to guys at the gun club, all agree on this point.
It's not *impossible* you get off on self defense, sure. But it's also not something you should bank on. If the guy had a gun pointed at you, you'd most likely get off. But if, after all is said and done, the guy only had a knife that you thought was a gun, or any other of the million mitigating factors that play into real life situations come into play, there's a very good chance you are facing a murder charge.
The statement "Ontario allows for lethal force in self defense" is not strictly false but it's HORRIBLE legal advice, and asking for jail time. I don't want to be convicted of murder like others have.
https://www.kruselaw.ca/library/using-reasonable-force-to-defend-myself-or-my-property-kruse-law.cfm
"Canadians have a right to defend their property or themselves as long as their defensive actions are reasonable under the circumstances. This means that if you injure an intruder entering your home or property, you would need to show that the circumstances gave you no other reasonable choice. Essentially, you can use whatever force is needed to prevent someone from unlawfully entering your house or from hurting you, but not more. The use of lethal force would generally only be appropriate in a situation where you had cause to perceive a threat to your life or of severe bodily harm, and had no other reasonable options for defending yourself."
Is a man charging at me or my daughter a situation wherein I had "no other reasonable options for defending myself"? Not to most Ontarians (jury) and not to many judges. You'd better ascertain he has a deadly weapon before you just blindly shoot him for entering your house. If you have time for that. If he's charging you, sure, shoot him. Then go to jail while they sort it out. It's revealed he's just a crazy local with a history of drug abuse, who was unarmed. Now you killed an unarmed man in Ontario.
That's almost certainly manslaughter at best, murder at worst. Ontarians HATE handguns. Use a handgun in this fashion and good luck avoiding a murder charge or a sentence for manslaughter or murder.
It's easy to say stuff on the internet. But go ask an Ontario criminal defense lawyer, a cop, or anyone who's seriously into guns and you'll get very different opinions than what you just wrote. Best case scenario is "maybe you get off at trial, maybe you rot in jail - it depends on a lot". A stranger entering your house only allows you to use the minimum amount of force to keep him out. You can barricade doors and push him out if he gets in. You'd probably get off easy for assaulting him with hands and feet. A weapon? Now the courts decide if that weapon was necessary to get him out. A gun? More so. A gun discharged and killing the intruder? You've got legal problems now.