What happens if you roll a critical threat, but then when you go to confirm the critical, you roll a 1, HOWEVER your various bonuses added to the 1 exceed the target AC?
Is it a critical or not?
It is not a crit.
It is not a crit.
I could be wrong but I do not think you can auto fail a crit conformation roll. IF that is the case then as long as your roll exceeds the target armor class even if you roll a 1 it would be a critical hit.
Critical Hits: When you make an attack roll and get a natural 20 (the d20 shows 20), you hit regardless of your target's Armor Class, and you have scored a “threat,” meaning the hit might be a critical hit (or “crit”). To find out if it's a critical hit, you immediately make an attempt to “confirm” the critical hit—another attack roll with all the same modifiers as the attack roll you just made. If the confirmation roll also results in a hit against the target's AC, your original hit is a critical hit. (The critical roll just needs to hit to give you a crit, it doesn't need to come up 20 again.) If the confirmation roll is a miss, then your hit is just a regular hit.
Attack RollAn attack roll represents your attempt to strike your opponent on your turn in a round. When you make an attack roll, you roll a d20 and add your attack bonus. (Other modifiers may also apply to this roll.) If your result equals or beats the target's Armor Class, you hit and deal damage.
Automatic Misses and Hits: A natural 1 (the d20 comes up 1) on an attack roll is always a miss. A natural 20 (the d20 comes up 20) is always a hit. A natural 20 is also a threat—a possible critical hit (see the attack action).
That second roll is still an attack roll.