A phrase that always bothers me is "To form a more perfect Union" from the preamble to the United States Constitution.

Perfection is absolute. If something is perfect, it has no flaws and cannot be improved upon. Words like "perfect" or "unique" cannot be modified with "more" or "less".
If something can be made more perfect, then it wasn't perfect in the first place.
If something can be made less perfect, then you must introduce flaws which will render it no longer perfect.
The same is true of "unique".