There is little that the West can do other than sanctions in the short/medium term, but they have to be hard and united. NATO troops and direct military action is not an option given the potential for spread to other countries and a huge death toll because of the mindset of the leader. In the longer term energy policy will need to change, especially in mainland Europe, to be less reliant on such an unpredictable country, and unfortunately all European countries will have to consider spending even more money on defence, including on NATO. Putin's government only respects military strength.
The downside to all this will be that it will push Russia even closer to China, but I believe that is inevitable anyway and something we are going to have to live with.
In the UK we need the ambition to spend serious money on renewable energy such as tidal power, and, even though this will displease many, I believe fracking will come back on the agenda.
I have a faint hope, but accept the naivety of it, that the people of Russia will turn against him when they realise the enormity of what is going on, and even that the people of Belarus, who are not exactly in love with Lukashenko, might rebel against being a poodle of Russia. I fully accept the remoteness of these possibilities.