In my opinion, there is only one way to defeat Putin and that is to compel the Russian people to overthrow him. And the only way to do this is to hurt the Russian people. And hurt them profoundly. This is horrible, but it's the only strategy that can work.
Putin is genuinely insane enough to use nuclear weapons. He doesn't want to, and he's hoping the threat of their use coupled with the West's understanding of his temperament will be sufficient. Yes, it could be a bluff, this isn't a game that can be played. The stakes are humanity itself. Putin has staked his entire being on this. He will not back down. He is not going to let any external force stop him. If he is going to fail, he is going to die and take as many people with his possible, in order to 'punish' them.
Attacking him via his wealth - via his oligarchs and freezing his assets - won't work, because this isn't about wealth, but about power and empire. He's quite confident that in time, when he's got control of Ukraine and a number of other nations (because he won't stop at Ukraine) he'll have more wealth than he does right now. Plus, he's hidden his wealth insanely well. It's next to impossible to find, let alone fully freeze. People all over the world have been trying to find it all for decades.
So, the only way to stop him is to weaponise his own people, the one country he cannot and will not nuke. Russians around the world are going to be deported. No Russian athletes in any sport or any form of international endeavour. Unilaterally expelled from the UN, even if that requires dissolving the UN and starting afresh. They must be brought completely and utterly to their knees. Yes, this is horrible, but Putin is backing the entire world into corner. He must not be allowed to succeed.
The Russians are a tough people who've endured much, but they have a breaking point. We've seen it play out in their history numerous times. They lives are going to become harder and harder as an overwhelming number of sanctions begin to bite. If this is sustained for long enough - and it's going to be hard to do when the suffering becomes visible - they will snap. Putin will be overthrown and (I think) ultimately executed by his own peoples, likely as not on war-crimes grounds, assuming they give him a trial of any form, that is.
Once the Russian people overthrow and/or kill Putin, the sanctions must not only be immediately reversed, but the scale of aid and international support given to Russia and its people needs to be unprecedented. The world cannot make the same mistakes that it did in Germany in the aftermath of World War I. The Russian people are not responsible for what their deranged President is doing, but for better or worse, they are the only ones who can stop him.
Before this is over, many countries will suffer. Germany, for example, gets 40% of its gas - a primary source of power - from Russia. It's not alone. As part of a coordinated plan, all countries that are in any way dependent on Russia must be immediately mobilising their resources to circumvent this problem. But it's going to really suffer before it's done. All nations are going to feel some pain. Such are the consequences of the actions of one despotic lunatic. I think some world leaders are still coming round to this reality.
To me, this is the best and most logical way for this situation to end. And it will still include the deaths of many thousands and the suffering of millions, especially in Russian. Ukraine will fall before this is over, but it will become a sovereign nation again in time. But if it happens, if I am right, we might avoid World War III. And as Einstein once mooted, if there's ever a World War IV, it'll be fought with sticks and stones, because that will be left.
My thoughts and prayers are with all Ukrainians, and with collective humanity as well.