User blog comment:UnlimitedMoeWorks/Touhou Characters and Their Likely Opponents/@comment-24106025-20190314161412/@comment-27033016-20190314221111

Thank you for the suggestions. Even I don't know who most of these characters should fight, so help is appreciated.

Look, I get Flandre Scarlet is a really, really popular character, but since she has only made one appearance as an extra stage boss in Touhou 6, and has yet to make any official playable appearance in any games so far, she sadly doesn't make the cut as a viable combatant. Her power to destroy anything is even just conjecture at this point since we don't know it's full potential. Can she really destroy planets? Is her power DBZ levels like her fans claim it to be? Unfortunately, we don't really have an answer to that so they're just fan speculation. The only thing that's confirmed about her power is that she can make people go kyuu~ (translation: explode), but other than that, she barely has any canon feats to go by. Her sister Remilia, by comparison, has a lot more to work with. Also, if Flandre really is that strong as her fans claim, she would have no problem destroying the entire Scarlet Devil Mansion caging her in the first place, which she has yet to demonstrate.

Kaguya is sort of an interesting case because being immortal, she could theoretically be on the same level as Mokou. However, this is held back somewhat by the fact she has yet to make any playable appearances, so the full scope of her powers has yet to be expanded beyond just her boss appearance in Touhou 8.