For those wanting to involve NATO and set off WW3 along with the nuclear apocalypse, I wonder - why the rush? We can still nuke this planet's civilization to scraps after Russia's/Putin's plans for re-establishing the "Great Russian Empire" have materialzied - or rather, if they actually do.
Please excuse my cynical undertone, but this reckless calling for intervention that may very well lead to a kind of catastrophic escalation that human history would never ever recover from REALLY scares the shit out of me :(
1) Atrocities are being committed and innocent civilians are being killed right as you type this tone-deaf question.
2) Appeasing dictators only leads to escalation, and early intervention minimizes damage. This is not theoretical, just look at Putin's belligerent last decades.
3) The risk of Russia unleashing nuclear Armageddon over Ukraine is very small. For all intents and purposes the West is already involved militarily - doing so overtly would not fundamentally change the equation.