not a defi expert, but I think the most common way to do this is to use Aave:

  1. borrow Tether
  2. swap it for USDC (or stablecoin of choice)
  3. wait for Tether to crash
  4. pay off your Tether loan at a fraction of its original value

risk is that your tether loan will be accruing interest (currently 1.4%) so if it doesn't crash or takes too long to crash you could be liquidated.