百依百顺 (bǎiyībǎishùn): docile and obedient

Recorded in Ming-dynasty 凌濛初's 《初刻拍案惊奇》 (Slapping the Table in Amazement, First Collection): 做爷娘的百依百顺 — 'parents who comply with their child in everything'. The 百...百... pattern (literally 'a-hundred X, a-hundred Y') intensifies both verbs into 'in every way'.

register

Often slightly negative: it implies excessive submissiveness or spoiling, not healthy cooperation. Compare neutral 听话 tīnghuà (obedient) with this stronger doormat-like nuance.