As far as rejection letters go, the one I almost never use is unfailingly polite.
It’s apologetic. It blames a “system” in which the deck is stacked against you, the consumer, for my failure to accept a case. And it offers several other options, including small-claims court or a credit-card dispute, as possible alternatives.
But a few weeks ago on this site, I confessed that I hate using the rejection letter when someone turns to me for help as a consumer advocate.