For the S&P there 3 big ones are
SH – 1x short S&P daily
SDS – 2x short S&P daily
SPXU – 3x short S&P daily
returns for these are generated using derivatives. I.e. short term index puts and calls. They theoretically could go to zero but it’s unlikely. The market as a whole would have to move more than it’s ever done in a single day to the upside.
Basically suppose you had the following scenario in the S&P
day 1 = -1.0%
day 2 = -0.5%
day 3 = +0.7%
day 4 = -1.5%
day 5 = -1.0%
If you used Sh and the shares were $20 when you bought them you would end up with the following.
day 1 = $20.20
day 2 = $20.30
day 3 = $20.16
day 4 = $20.46
day 5 = $20.67