我以为你刀枪不入我以为你百毒不侵
[wŏ yĭ wéi nĭ dāo qiāng bù rù wŏ yĭ wéi nĭ băi dú bù qīn]
A direct translation would be 'I thought you were impervious to weapons, I thought you were immune to all toxins.', metaphorically implying someone believed the other person to be invulnerable, not easily affected emotionally, or strong beyond measure.