She Who Must Not Be Named

Proper Noun.

She who must not be named is the author of the book series Harry Potter. In 2020 she officially outed herself as a TERF after defending several "mistakes" with trans community.
As a result of being a TERF the Harry Potter fandom no longer cares to even mention her by name. Her new name is inspired by he who must not be named who is the arch-villain, Lord Voldemort, in the book series.

An ex's name so vile and foul that saying the name conjures an evil so dark and black that the sun is blotted from the sky and it rains blood for a full week. By uttering her demonic handle your tongue splits in two and rots from your mouth then you instantly hear all of humanity cry out with sorrow. Babies, children and small animals die once they hear her heinous name. El Diablo trembles at the smallest whisper of this being’s moniker. This foul being casts no shadow. You are warned, never mention that sick cruel name.

JK Rowling.

An ex whose mere mention floods your mind with what could have been.

She created a horcrux when she left you.