She-Who-Must-Not-Be-Named 

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

She created a horcrux when she left you.

She-Who-Must-Not-Be-Named's art adorns the walls of my aunt's house.

She-Who-Must-Not-Be-Named by Prathamensch February 5, 2017

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.

I look up to Emma Watson and not she who must not be named.

She Who Must Not Be Named by MDooley47 June 15, 2020

She who must not be named

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.

"Hey dude what ever happened to your ex (wife or girlfriend)? Wasn't her name..."

"STFU! Never mention 'she who must not be named' I'd like to keep my sanity for a little while longer, thank you."

She who must not be named by CERT May 7, 2014

She Who Must Not Be Named

JK Rowling.

I'm gonna start referring to JK Rowling as She Who Must Not Be Named.

She Who Must Not Be Named by Barty Crouch Jr January 28, 2021