NATO should start flying planes all over his borders.
What planes? NATO's available air force is appallingly dismal.
If WW III started tomorrow Russian forces could overwhelm and devastate Eastern Europe before--and here it comes--the US stepped in and paid the bill with US blood and US taxpayer money.
Ukraine and weapons? If the US begins openly weaponizing Ukraine's military Putin will respond in kind and escalation will occur, and probably to a very bad end.
Putin is surrounded and kept in power by super wealthy oligarchs. These men are not interested in nationalism per se. They are interested in maintaining monopolies over the Russian citizenry they exploit to keep and grow their economic power. Controlling these men is controlling Putin.
How to best influence Russia's oligarchy is the quadrillion dollar question.