If you say that something is unforgivable, you mean that it is very bad, cruel, or socially unacceptable.
例句
These people are animals and what they did was unforgivable...這些人是禽獸，他們所做的一切都是不可原諒的。I also suspect that I'm becoming a bore, which is something unforgivable in anybody, but especially in a journalist.我還懷疑自己正在變成一個令人厭惡的人，這對任何人來說都是不可原諒的，對于一名記者而言更是如此。