Fanaelialae
Legend
Bounded Accuracy presumably renders it unlikely you'd have only-hit-on-20 attacks. IIRC, 5e crits don't happen on a 20 when you only hit on a natural 20, but I could be thinking of one of the playtest packets...
This.
Although I do believe that rule didn't make the final cut. Easy enough to house rule though.
With bounded accuracy, only being able to hit on a nat 1 or only being able to hit on a nat 20 are outliers. Possible, but pretty rare (typically only when facing very low level enemies with very high level characters). In 3e, modifiers could balloon so rapidly that this situation was far from uncommon.