Let's play a game:

Take your waifu, wherever she might come from, and make a decent BBEG out of her

I change nothing.

Well she's already got a problem of bugfuck crazy bloodrages due to the influence of an ancient Japanese snake deity, so really all it takes is saying that she's pretty much stuck in that state.

The secret wizard that created this dungeon

But user, my waifu is already the mastermind behind the BBEG.

...

I can't do it. She's too good. Too pure.

Kinda difficult to do. Maybe as a physical/social adept in Shadowrun as a minor villain. But my waifu choices don't make good major ones.

Like in every other setting, it's some fucking elf's fault

Finds out about witches, succeeds in shooting the rest of the team, then doesn't kill herself, instead deciding to go on a crusade to kill every last magical girl on the planet in order to get rid of witches.