Vagabond's Story Recommendations (Patreon)

Theme: Youjo Senki

A Young Girl's Nuclear Armageddon 

A Young Girl's Weaponization of the Mythos 

And, of course, if you haven't seen the actual story that inspired these fanfics, check out Youjo Senki, or the Saga of Tanya the Evil. The manga and anime is easier to approach than the light novel.