They should be confiscating all assets of Russian nationals and companies outside of Russia, period.
Western multinational companies have to leave Russia or be banned from doing business outside of Russia.
Arrest all Russian government officials outside of Russia. UN convoy, Russian diplomats. Confiscate their assets.
Impose a travel ban on all Russian citizens. Freeze assets of all financial institutions that use the SPFS payment system.
Cancel all flights to/from Russia. Issue an international arrest warrant for Putin, his family, and his associates.
The question I suppose is how much does any of this actually harm Russia, and does it harm the west too?
Putin isn't really dependent on a network of allies, I would assume that Russian government officials are mostly replaceable 'yes men'.
An international travel ban, cancelling flights etc., would probably be met with a shrug of the shoulders. Russia would respond tit-for-tat by banning all western flights over its own ludicrously vast airspace, which would hurt the west.
An arrest warrant probably wouldn't bother him either.
Blocking Russian gas/oil sales harms the west.
Trying to cut Russia out of the financial system means they'll probably just cozy up to China some more.
I'm certainly no expert on any of this, just trying to understand what his limits are or what possible western response could cause him any concern at all. The only thing is NATO countries sending in troops, which seems very unlikely. So what's left? The west providing background support to the Ukranians, leading to some horrible attritional war that could continue indefinitely.