The best hand sanitizer for COVID-19 should meet both the CDC and WHO guidelines for killing COVID-19 and other coronaviruses. Both the CDC and the WHO recommend that hand sanitizer contain at least 75% alcohol in the finished product. The higher the alcohol concentration, the better it will work. An 80% alcohol hand sanitizer will work better than a 75% alcohol hand sanitizer, and anything below 75% has not been shown to kill COVID-19 within 30 seconds in all environments. Further, a gel based hand sanitizer will spread more evenly on hands than a water based sanitizer, helping to ensure the COVID-19 virus will be inactivated completely without any missed spots. Keep in mind that Isopropyl Alcohol is generally sold in concentrations of 50% – 91% alcohol. So a 75% Isopropyl Alcohol solution alone would work, but mixed with other ingredients to form a gel, the alcohol concentration will diminish and drop below CDC guidelines.

Therefore, the best hand sanitizer for COVID-19 is an 80% alcohol gel based hand sanitizer.

CDC: Centers for Disease Control Guidelines

According to the Centers for Disease Control (CDC), hand sanitizer should contain at least 75% alcohol.
https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/cleaning-disinfection.html

WHO: World Health Organization Guidelines

According to the World Health Organization (WHO), hand sanitizers should contain between 60% – 80% alcohol.
https://www.who.int/docs/default-source/inaugural-who-partners-forum/who-interim-recommendation-on-obligatory-hand-hygiene-against-transmission-of-covid-19