less active or intelligent than you are at other times

I'm at my worst first thing in the morning. 我早上的时候状态最差。

showing the most unpleasant side of someone's character

This problem over late payment has shown him at his worst. 这次拖延付款的问题使他原形毕露。

used to say what the most unpleasant or difficult situation could possibly be

At worst, she can only tell you off for being late. 充其量她也就是会责备你迟到而已。

considering someone or something in the most negative or unkind way possible

She is at worst corrupt, and at best has been knowingly breaking the rules. 她最坏的情况是腐败，而最好的情况是故意违反规定。