Why is it that in every fanfiction I've read the main characters ex is a terrible person/an asshole?
Like, why?
Not all exs you'll have are bad people! Maybe you two just found people that are better for you, maybe you two just didn't work out.
There's no need to make them a terrible person.

And their ex is ALWAYS a dude.
COMMON MAYBE THE READER HAS A GIRL EX HMMM???

EVEN IN THE X FEM!CHARACTER STORIES THEIR EX IS A DUDE!!!