Critical Hits
Source Player Core pg. 253
When you make an attack and succeed with a natural 20 (the number on the die is 20), or if the result of your attack exceeds the target's AC by 10, you achieve a critical success (also known as a critical hit).
If you critically succeed at a Strike, your attack deals double damage. Other attacks, such as spell attack rolls and some uses of the Athletics skill, describe the specific effects that occur when their outcomes are critical successes.
If you critically succeed at a Strike, your attack deals double damage. Other attacks, such as spell attack rolls and some uses of the Athletics skill, describe the specific effects that occur when their outcomes are critical successes.