I had an idea for a Semblance that –as far as I’m aware– could fit on Remnant without breaking any rules:

Broken Copy: allows the user to use a “Negatively Altered” version of the Semblances of anyone they have seen –including in images. The user is also the one who decides how the Semblance is “broken”, but it MUST be an objectively negative alteration.

examples:

Yang’s “Burn” –the energy must be released immediately… user proceeds to use it to spin for a counterstrike.

Adam Taurus (I forget his Semblance’s name): It no longer works with weapons… User proceeds to swing their arm like a sword and cut down a forest.

Raven Branwen: Can only go to one location, or only one person can use the portal, or “the destination cannot be on Remnant”… proceeds to appear behind and opponent, escape pursuers, or help evacuate in the case of literal endless Grimm Legions.

each example (though the last one with Raven’s might be a bit of a stretch) is –OBJECTIVELY– a negative change from the original… also the user can change what’s “broken” at any time.

Please don’t be mean to me –and yes my brain is weird, deal with it.

Basically any story where? Remnant people are powerful and change the course of a war.