How it works
Personal Liability is a mandatory Hell Mode modifier that removes the short automatic invulnerability normally granted after receiving a burst of damage. This condition is not available on standard save files.
Practical strategy
Treat every rapid follow-up attack as more dangerous; leave safe space after taking a hit and avoid exchanging damage with groups.
Common mistake to avoid
Assuming you can disable Personal Liability in Hell Mode, or enable it on a normal save.