An important protocol was Luna, before it collapsed in 2022.
UST was an algorithmic stablecoin. To create UST you had to burn Luna, and for UST to retain its peg, one UST could be changed for $1 worth of Luna at any time. On May 7, over $2 billion worth of UST was unstaked, and hundreds of millions of it were quickly liquidated. The huge sell-offs brought down the price of UST to $0.91, from $1. As a result, traders started to change 90 cents worth of UST for $1 of Luna. This was a huge arbitrage opportunity, after all. More and more people sold off UST for Luna, which led to the minting of more Luna and an increase in the circulating supply of Luna, driving down the price of Luna itself.
The Luna collapse was a massive event in 2022. When the Luna ecosystem collapsed, it’s estimated that $60 billion got wiped out of the digital currency space.