万箭穿心百毒不侵
[wàn jiàn chuān xīn băi dú bù qīn]
This online name 'Thousand Arrows through the Heart but Immune to All Poison' signifies that despite having been hurt deeply (like pierced by thousands of arrows), one is unyielding and unaffected by any form of temptation or adversity (like immunity against poisons). It implies an extremely resilient and unassailable state of mind.