liar

I knew he was a liar when his story changed three times in one day.

(Chinese) 当他的说法在一天内变了三次时，我就知道他是个说谎者。

Nobody trusts a known liar, even when they are actually telling the truth.

(Chinese) 没有人会相信已知的骗子，即使他们真的在说实话。