USD Tether is a Bitfinex issued ERC-20 token which is claimed to be backed by dollar at 1:1 ratio. There are controversial opinions about this and some say it's a scam.
Do you trust USDT or believe it might be a scam?
For me it is one of the most reliable.
But I still remember when they themselves could have participated in the 2017 bitcoin bubble.
It is still a question to be solved ...