“Incredible” could express disappointment or anger as well as when finding something great ,extremely good ,amazing and marvellous. Unbelievable” is also used informally to emphasize that something is good and impressive or bad.
They always have incredible stories to tell.” ( surprising)
It is incredible ,how could she cheat on him!.” ( expressing disappointment or anger.)
He played an unbelievable match.”
He earns an incredible amount of money.
My performance at the Christmas concert was unbelievably bad.’