unbelievable

adjective [原级]不可信的，不真实的；难以置信的，特别的；极其糟糕的，令人震惊的；极好的，好得令人难以置信的

You can use unbelievable to emphasize that you think something is very bad or shocking. ^{(糟糕得) 令人难以置信的•  I find it unbelievable that people can accept this sort of behaviour.}