The political and military leaders of Ukraine seem as worried about their allies as they are about Russia.

A key Ukrainian national security official sat down today and told the country’s allies what they could do to help: please, calm down.
...
Reznikov, the defense official, told the BBC that he did not regard the collection of Russian forces stationed along the Ukrainian border as enough to stage an invasion.
“This is their territory, and they have the right to move to the left, and to the right,” he said. “Is it unpleasant for us? Yes, it’s unpleasant, but it’s not news to us.”

Ukraine President Zelensky said the decision by the United States and United Kingdom to withdraw some staff from their embassies in Kyiv was a “mistake.” He also said that he is ready to meet with President Putin and that the "sanctions are not designed for our country to help our country."
But the really big statement Zelensky made that barely got noticed was this:

Zelensky was also blunt about NATO's role in the crisis, declaring (in a line that Vladimir Putin would also agree with): "Tell us openly we will never get into NATO."

Russia would stand down if NATO would simply do that.
The warmongers that dominate the media in Washington and London have absolutely no intention of calming down. Their eyes are focused squarely on the thing that is closest to their hearts - carnage. Lots and lots of other people's bloodshed. Poor people's bloodshed.

However, no matter how much they might want to, they can't just start carpet bombing Russian cities. This isn't Serbia, Syria, or Iraq. Russia can fight back.
Thus the warmongers have to go through the steps before. One of the most important steps is economic sanctions. Fortunately, for them the sanctions step is already largely exhausted. There is really only two sanctions still available.

#1 Sanction Putin personally

Joe Biden has said he will consider personal sanctions against Vladimir Putin if Russia invades Ukraine, as western leaders step up military preparations and make plans to shield Europe from Russian gas being cut off.

The downside of this would mean that it would effectively kill all diplomacy with Russia. If you wanted a war, this would be the way to go about it.
But it's #2 that is getting the most attention.

#2 Cut Russia off from SWIFT

London (CNN Business)Some are calling it the "nuclear option."

That is literally the first sentence.
Here's a Pro Tip - If you were ever considered a foreign policy action with a major nuclear power, and the action had the nickname of the "nuclear option." Then it's a bad idea.

As Western governments threaten Russia with a package of unprecedented sanctions aimed at deterring President Vladimir Putin from ordering an invasion of Ukraine, there's one measure in particular that appears to strike fear at the heart of the Kremlin: cutting the country off from the global banking system.
US lawmakers have suggested in recent weeks that Russia could be removed from SWIFT, a high security network that connect thousands of financial institutions around the world.

This sanction would indeed cause a great deal of pain in Russia, but it wouldn't destroy Russia. It would have an immediate reaction.

Senior Russian lawmakers have responded by saying that shipments of oil, gas and metals to Europe would stop if that happened.

"If Russia is disconnected from SWIFT, then we will not receive [foreign] currency, but buyers, European countries in the first place, will not receive our goods — oil, gas, metals and other important components," Nikolai Zhuravlev, vice speaker of Russia's upper house of parliament, said Tuesday, according to state media outlet TASS.

That's not 100% true, but it's mostly true, and that means incredible suffering in Europe as well.
Russia supplies around 40% of Europe's gas, and this couldn't come at a worse time.

As of December 2021, storage levels are below the minimum volume recorded for this time of the year in any of the previous five years. In mid-December 2021, Europe had 690 TWh of gas in storage. On average from 2016 to 2020, it took until the third week of January for reserves to drop this low...
European gas production has decreased in the last few years because of the closure of gas fields.

Without SWIFT it would be difficult for any country to buy Russian goods. America is trying to organize natgas exporters to meet this shortfall, but it is a doomed effort. There simply isn't enough infrastructure to switch from pipeline to ship.
Even if there was enough infrastructure, natgas being shipped halfway around the world is going to cost significantly higher. So cutting Russia off of SWIFT is going to cause almost immediate suffering in Europe, and that's only the short-term.

Of course it will also cause immediate suffering in Russia.

"The cutoff would terminate all international transactions, trigger currency volatility, and cause massive capital outflows," Maria Shagina, a visiting fellow at the Finnish Institute of International Affairs, wrote in a paper last year for Carnegie Moscow Center. Excluding Russia from SWIFT would cause its economy to shrink by 5%, former finance minister Alexei Kudrin estimated in 2014.
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There is precedent for removing a country from SWIFT.
SWIFT unplugged Iranian banks in 2012 after they were sanctioned by the European Union over the country's nuclear program. Iran lost almost half of its oil export revenue and 30% of foreign trade following the disconnection, according to Shagina.

So there will be short-term pain all around, including in the U.S because German and American banks are the most frequent SWIFT users to work with Russian banks.

After the short-term pain is over, the real consequences begin.
Russia has been planning this for eight years.

Russia has taken steps in recent years to blunt the trauma should it be removed from SWIFT.
Moscow established its own payment system, SPFS, after it was hit by Western sanctions in 2014 following its annexation of Crimea early that year. SPFS now has around 400 users, according to Russia's central bank. Twenty percent of domestic transfers are currently done through SPFS, according to Shagina, but the size of messages are limited and operations are limited to weekday hours.
China's fledgling Cross-Border Interbank Payment System, or CIPS, may provide another alternative to SWIFT.

Russia has also managed to eliminate U.S. dollars from their economy. Foreign Exchange Reserves in Russia reached an all time high in December of 2021.
While also eliminating dollars from their arms export deals.

The Economist was very clear about the danger of this move.

America’s foes would rush to alternatives, hastening its financial decline

Recall that the EU created INSTEX when Iran was kicked off of SWIFT. So while the EU didn't really use it (except as a test) the mechanism already exist to get around the U.S. sanctions.