no, i mean the debtor.
You talkin' like a UCC Art. 9 security interest? I'd never really thought about it. What happens if there's still a deficiency? Do you mean to tell me you can grab my stonks, then I have to pay taxes on the "realized" "gains," then I still owe you money?
if we're still talking about loans to the uber rich guaranteed by liquid assets, i'm fairly confident that those loans are made at a small fraction of the asset value and have covenants that would force action long before those assets would be insufficient to cover both the debt and possible taxes.
if we're talking bankrupcy or something like that, i think the assets would probably have a tax lien on them prior to sale? i dunno, i'm not the lawyer here.