It's not just put/call ratios that are at extremes. A full listing would be redundant; here are four examples:

The percentage of AAII investors that are bullish is just 18%; it has only been lower once in the past 20 years (the April 2005 low in SPY).

An average of more than $6b has flowed out of equity funds in the past 5 weeks; since 2003, the only times outflows have been greater were in 2008 and at the market lows in March 2009 and late August 2011.

Only 20% of S&P companies are above their 200-ema; in the past 16 years, the only times it has been lower was during the 2002 and 2008 bear markets and at the market lows in August 2011 and 2015.In the past 20 years, the daily MACD for SPY and NDX has only been lower once, during the late-2008 meltdown.

While it's true that bear markets feature in the list above, most of these extremes occur within the context of a bull market. Take the AAII bull ratio, for example. Over the past 25 years when the ratio is less than 30% (like now), the S&P has been higher both 3 months and 12 months later 90% of the time. Similarly, the Citibank Panic/Euphoria model is now at a level where equities over the past 30 years have always been higher a year later