at heart
本质上的
A：Ben always appears rude to the people around him.
A: 本总是以周围的人表现得很无礼。
B: But he's really kind at heart.
B：可他事实上是个很善良的人。
A: That's true. We can't judge people by appearance.
A：是的，我们不能从外表来判断人。