So I'm wondering what kind of unprecedented economic sanction can be given to Russia if they continue to evade Ukraine.
Sanctions: United States strategies to make sanctions against a country are economic, political, bank or stock market sanctions that can cause severe inflation to the country, it's US method and Strategy, however, it applies to other weak countries, as we know US officials will take action against Russia for invading Ukraine, US will plan to burden Russia's economy.
Wait a minute, Russia is not a weak country, Russia is a superpower, they are not afraid of sanctions and threats from US officials, history has proven until now that Russia is not easy to give up in this matter, if the US does as I said above Russia can hit back and hit the US economy, as I know gas for Europe is supplied from Russia, they can cut shipping and increase cyber attacks on European and US infrastructure too, they are not the type to submit to other countries, they have the weapons to counterattack their opponents.
In my opinion, if the US can impose sanctions on Russia, Russia can counterattack, they will destroy global economic stability.
conclusion: the sanctions that the US wants to carry out against Russia could have a bad impact globally including America, America picked the wrong opponent this time.
You forget about the Russian "big brother" - CHINA. The fate of Russia, in fact, depends on the position of China. And if now China decides that it needs Russia, but as a donor of resources or territories, then tomorrow Russia will cease to exist and become a new region of the PRC. Stories about a "strong economy" and the same fabulous "strongest army" of Russia are a myth. The only real threat from the Russian Federation is the remnants of nuclear weapons, everything else is "wearing the clothes of the deceased grandfather", i.e. the USSR