Okay so how do stop Russia from just taking Ukraine just because it wants it... in a way that in anyway makes Russia (or China or anyone else) think twice about doing it the next time.
There seems to be no "found out" to Russia's "**** around."
Short answer: There are no guarantees. If there was some magical 100% clear method being the most effective, we would use it every time and wouldn't even be in this situation. If good always triumphs over evil, there wouldn't be any evil.
Longer Answer:
People jump straight into "Nuclear War" but there are several steps that need to happen before this is a thing.
1) The bad guys need to have nukes
2) Said nukes need to be effective and functioning
3) Bad guy has to actually be willing to use these nukes
4) Bad guy will need to have the order passed through the chain of command and every single person in the chain of command need to be willing to pass the command to fire - or in case he isn't then he needs to be dealt with and replaced.
5) No outside (to the chain of command) interference prevents the actual button from being pressed.
We're all operating the assumption that #1 is true and that's fine.
#2 - frankly considering the existing situation of their military, I'm starting to wonder about this one as well. If their tanks are so badly maintained, why do we assume their nukes are properly maintained?
#3 - Let's assume he is indeed mad enough to want to use them.
#4 &5 - is where I think the current course of action is.
The idea is that Putin himself might be a mad man willing to blow up the whole world is a given. But are we absolutely certain that all of his subordinates are?
If he loses control over his people, he loses control over his weapons as well.
The whole point of sanctions is to get the message to his people of what is really going on and point out who is the bad guy.
As someone else said in this thread, telling them they won't be able to see the new Batman movie sounds pointless, but it does send them a message.
The current plan is essentially to make things so bad over there that the people would either revolt or at least let them think twice if it's worth destroying the human race over his megalomania.
Not to mention, most people would follow his orders knowing that if they don't - they die. But if a nuclear war starts they are likely to die anyway - they might start to think twice that perhaps following his orders are the least likely chance to survive.