我百毒不侵但早已万箭穿心
[wŏ băi dú bù qīn dàn zăo yĭ wàn jiàn chuān xīn]
This username translates to 'I'm Immune to All Poisons, But Already Pierced by Ten Thousand Arrows'. It reflects a persona that pretends to be tough and unaffected on the outside, but has experienced deep emotional wounds or betrayals.