his bark is worse than his bite 刀子嘴，豆腐心

【例句】
I wouldn't be scared of her if I were you. Her bark's a lot worse than her bite。
如果我是你，我不会怕她。她是个刀子嘴，豆腐心的人。

His bark is worse than his bite.
他嘴坏心不坏。