It can't be "really" one-of-a-kind, any more than it can be "nearly" one-of-a-kind.

I know that's the standard riposte, but I don't buy it. What does it mean to be unique? It means that, in some notional morphological space, it has a nonzero distance to its nearest neighbour. I think it's valid to say "really unique" if that distance is relatively large.

A point object cannot be "slightly" in France, but it can certainly be "nearly" in France, or, if a long way from the border, "really" in France.

I've got similarly little patience for people who insist that the word "literally" cannot be used metaphorically.

Peter