melt down (someone's) defenses

Translations
разрушить (чьи-то) обороны
Her kindness and patience eventually melted down his defenses.
Ее доброта и терпение в конечном итоге разрушили его обороны.
Definitions
To gradually weaken or break through someone's emotional or psychological barriers, making them more open, vulnerable, or receptive, often through kindness, persistence, or emotional influence.