Europe remembers the murders, destruction and subjugation of WWII, and history is now repeating itself in Ukraine. NATO countries have to vastly increase their militaries, both defensively and offensively, to thwart Russia. Tactical nuclear missile systems should be deployed within NATO countries. The addition of Sweden and Finland to NATO will give it strategic presence in the north.
Economic sanctions against Russia must be maintained for years to drive the Russian economy into a depression. This will hurt the civilian population, but it is necessary to deprive the Russian military of funding, and hopefully significantly degrade it over time; and Russia must pay trillions of dollars in war reparations to rebuild Ukraine.