She was not happy, to say the least. [=she was very unhappy]至少可以说，她并不快乐。

He is, to say the least, hopeful about the future. [=he is very hopeful about the future]至少可以说，他对未来抱有希望。

To say the least, they were disappointed that their trip was canceled.至少可以说，他们对取消行程感到失望。