It is a fiat pegged currency, so can it cost less than its pledge? Tether was accused of not having this collateral, but as I know there were several audits that confirmed that Tether had this sum of money.
There were cases when stablecoins collapsed, but there were algorithmic stablecoins that couldn’t fight against panic. The most important thing in crypto is trust. As long as people believe in Tether, there is no point in worrying.