Unloading a raft of targeted sanctions after months of perceived inaction against Russia by the Trump administration, it's becoming clear that Washington has hit the country where it hurts. The intended message is that no oligarch can escape economic punishment for involvement in the country's alleged transgressions.

Russian stocks suffered their worst day since 2014 as fears over recently-imposed U.S. Treasury sanctions swept the country. Monday saw Russia's main share index, the dollar-denominated RTS, crash 11.4 percent while the ruble fell 4.5 percent against the dollar on Tuesday.

Until recently considered a safe bet with many investors "overweight" on Russian assets, the country's markets now appear at the mercy of the U.S. Treasury, whose deployment of punitive economic measures Friday was its most severe — and most unpredictable — yet.

The gut-punch? Washington's secondary sanctions, which threaten to punish non-American individuals and companies doing business with the sanctioned entities in the same way they would Americans. This is a particularly powerful component of the sanctions placed on seven Russian oligarchs, 12 businesses and 17 government officials which were put on the Treasury's Specially Designated Nationals (SDN) list, freezing their U.S. assets and forbidding U.S. persons and companies from doing business with them.

Congress's sanctions legislation, CAATSA (the Countering American Adversaries through Sanctions Act) allows for the measures to be expanded as well, according to Max Hess, political risk analyst at AKE Group. Depending on the U.S. government's determination, he said, "They would apply in full to pretty much anyone — well, anyone hoping to ever use the U.S. financial system — as they would to a U.S. person or company, hence a big deal."

Several Russian entities and businessmen long serving as conduits for Western investment into the country now face crippling restrictions on their reach in international markets. And the sharp drop in domestic asset prices reflect growing fears that anyone could be next.