USDT is by far the most sketchy stablecoin out there. USDT currently has $76B in circulation and they claim it is backed 1 to 1 to USD, this would mean Tether has $76B cash reserves but it has never released an official audit.
Now the interesting or rather scary part is that every time there is a parabolic move by BTC, USDT issuance also goes parabolic, do they really have that much USD to back tether? Most likely no. USDT mimics USD and fiat's worst property i.e issuance out of thin air.
If and when this likely fraudulent company goes under, the biggest liquidity provider for the crypto market will cease to exist and the effects will be catastrophic. If anything we need to stop using USDT and move towards more transparent and decentralized stablecoins like DAI or UST (terra USD) or even USDC as a centralized stablecoin is a much better alternative than tether.