Out of all the legal actions taken against cryptocurrency companies by U.S. regulators and prosecutors this past year, one stands out. A potential crackdown on Tether Holdings Ltd. could really shake things up in the digital asset world.

Tether issues the USDT token. This token acts as a digital version of the U.S. dollar. Right now, it has a market capitalization of about $120 billion. That makes it the third-largest cryptocurrency by market value.

What's more, USDT is the most traded token every day. Why? Because it serves as a substitute for the dollar in markets where traditional currencies can't be used for transactions.

This situation is definitely worth keeping an eye on.