What's the Biggest Curveball in Stock Market?

In 1929, obviously we had a 17% drop. We had about a 50% retracement. And then we began to roll over and go down. When we went down, we literally stopped at Rasha Shana. In 2008, there was a massive curveball that came our way. Probably messed up with ton of traders. If that's all present, then those conditions are ripe where you could get a really extreme move to the downside which the public knows as a crash.