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...这些人是禽兽，他们所做的一切都是不可原谅的。I also suspect that I'm becoming a bore, which is something unforgivable in anybody, but especially in a journalist.我还怀疑自己正在变成一个令人厌恶的人，这对任何人来说都是不可原谅的，对于一名记者而言更是如此。