I have asked a question before about this Grave Cleric feature in the past, and was inclined to believe that you are able to turn critical hits into misses by way of the feature, but upon looking into it further, I found that adamantine still gets hit as in this question.
I have also found questions, like this, where it says Sentinel at Death's Door does not work on crits.
Is Sentinel at Death's Door able to cancel a critical hit into a normal hit and potentially a miss, and adamantine cannot? Or can neither do that?