Huh, I get to add this one...
Race: Half Elf
Class: Wizard 5/Riftwarden7 Tier 6 Archmage
Adventure: Demon's Heresy
Catalyst: A critical, max damage Mythic Enervation to the face.
Details: Our encounter through Xanthir Vang's lair was going fairly well, and we had an answer to everything he threw at us. Finally, in his anger (Totally justified, my character is always angering everything we fight), he fires off a mythic enervation. The DM rolls to hit, and cringes. Rolls again, confirming the critical hit. And as he rolls that D6, his eyes go wide...
After confirming that yes, enervate damage does double, and if a 12th level character has 12 levels drained, it's kinda hard to bring them back without higher level spells. Full disclosure, this is only the second time this DM has killed me, and both times he's had ways of bringing me back because he doesn't want to figure out how to bring in a new character. For this, he did not have it slay me outright, I was instead turned into a Juju Zombie. After Xanthir Vang fled, the party used the luck blade we had found to 1) undo the negative levels and then 2) revive me. Still, I figured being turned into an undead, then technically dying from having my undead state reversed would be a fun read for some.