百毒不侵然后不堪一击
[băi dú bù qīn rán hòu bù kān yī jī]
Literally means 'Impervious to all toxins, yet fragile at heart'. Such usernames reflect a duality where the individual pretends to be tough and immune to harm externally, whereas deep down they are very vulnerable. They appear unshakable or indifferent on the surface but feel weak or hurt under specific circumstances internally.