The thing that we all have to carefully consider, damage rolling in Pokemon since Gen 1 is random. This is something different from Critical Hits.
I remember those moments where I got KO'd not because of a critical hit but its because Damage rolls hated me and decided to let the AI get the 100% Damage Roll (When i mean 100%, the maximum possible amount of damage). Max damage rolls + Critical hit is something that makes this game so surprising at times.
Its even more hilarious when it happens for the player's favor. I had a moment of grace in Pokemon Y with the battle against Diantha when I used a Max Revive on my Lucario because i thought that I'm basically in the inevitable loss against her, with Mega Gardevoir wiping out most of my remaining party members before i used the Max Revive. So my max revived Lucario with Shadow Claw went up against the inevitable, Mega Gardevoir who could clearly defeat it with whatever STAB Move it had (Moonblast or Psychic, both of which will deal HIGH amounts of Neutral damage against the Fighting/Steel type either way) but i suddenly rolled a CRIT AND THE MAX DAMAGE ROLL on Mega Gardevoir, on a NON-STAB Shadow Claw and scored the KO on her, which i honestly thought would never happen. (The most that my Lucario at Lvl58 did to Diantha's Mega Gardevoir (lvl68) did most of the time was around only 80% of her Health or less).
Then there's also my moment with Battle Chatelaine Evelyn in AS who for some reason, her Primeape's Stone Edge was dealing disgusting amounts of damage to the point where it was OHKO's things without Stone Edge critting, and again, NOT ON STAB. Again, Damage Rolls...