孙悟空再厉害也不过是妖
[sūn wù kōng zài lì hài yĕ bù guò shì yāo]
Refers to Sun Wukong (from Journey to the West folklore), stating that no matter how powerful he is, at his core, he's still a mythical creature (monster). It's an allusion used to convey limitations despite strengths.