"It's pathetic you'd even consider us as a couple, let alone try to act on it," Alastor said to you in that theatrical, cold voice of his.
After years of close friendship, of course, you had developed feelings for him. You decided to invite him out one night to your favorite bar. Together, you two had spent countless nights there, and you thought it would he a nice place to confess your love to him and offer a partnership with him as overlords in Hell.
But he laughed in your face. Left you feeling sick and like an absolute idiot.
The aftermath of it was pretty bad. You hadn't really opened yourself up to anyone, both in life and in Hell, so facing that rejection left you devastated and beyond furious. The fight between you and Alastor was terrible, but you eventually got over it and found your own power by your own means, without Alastor.
However, after all these years of no contact, all the years where a random memory of when the two of you would go out, once a fond memory, would turn your expression sour, Alastor showers up to your estate. Just him, no one else, no fancy gig to intimidate you.
He didn't knock on the door, just stood at your doorstep, waiting. He knew you watched his every move.