The point is it does not matter that the kid has a horrible life. It's still bullying and attacking people and needs to stop. The first rule of helping a family member with depression or a friend lashing out in pain is protect yourself, otherwise you can't help anyone.

The situation would be different if e.g. Ukraine had invaded Russian territory after the invasion of Crimea, or had done broken armistices beforehand, or there had been a mass killing of ethinic Russians in Ukraine. There has not been. This means long before we can talk about Russia maybe feeling threatened by NATO expansion they need to stop the war they started.

There is no nuance here. Russia felt that for whatever reason an attack-war was warranted and couldn't even be bothered to come up with a believable justification. The fact that other countries have done the same thing (e.g. over allegations of WMD) changes nothing here.