Going back some way in the thread, regarding other loss conditions that are mechanical besides dead characters I would suggest some DM ingenuity, possibly with table/player input if thats your jam.
So a while back one character lost to a wizard who had shapechanged into a Marilith. Long story short the character was inflicted with a Nightmare condition which had the possibility of nullifying any resource gain from Long Rests.
Another is the Hideous Scarring from the Lingering Injury table in the 5e DMG. Pc gains Adv on Intimidation DisAdV on Persuasion. I let the PC decide the where and how of the scarring.
Sky is the limit with creativity in creating Loss Conditions with mechanical effects. I used some of the templates from DW on how PCs can recover from these conditions.
I've used perma death but it's usually rare for the main campaign characters (but not off the table).
We've also used death to explore duplicates due to timeline fudging, explore the City of the Dead in the Fugue Plane + Wall of Faithless and Cloning storylines. Haven't done Reincaration yet.