Sorry, let me correct myself, I am the one who gave various other people tragic backstories. (Ex-school bully)
local girls brain literally rotted away due to horniness and being terminally online. Wait, that's more of a newsstory
(Me now realizing @girlrotting was asking for a backstory FOR them, not that we tell them a random backstory.)
Robot assassin falls in love with their creator, but ends up killing them accidentally one day. But they never realize it, so they continue to interact with the rotting corpse as if it was still alive.