It takes a lot to describe a person as unforgivable, but when that point is reached, it is permanent. Once I label someone as untrustworthy or deficient, it sticks. I wouldn't really call it a grudge, though, since I don't harbour any feelings of hatred for that person- it's more like making a command decision that they can no longer be relied upon or socialized with on a close level. I try not to be hugged by them and avoid working with the person if at all possible, but I don't actively feel hate or act unfriendly towards them (well, any more unfriendly than I usually am).