Book where FMC has magic powers, everyone is afraid/cautious, only the villain helps her achieve the full potential of her powers

Hey everyone!

I was watching a video of The Book Leo where she mentions this trope (?) of a story where there's a girl who has magical powers but everyone of the "good" side is afraid or too cautious to let her use all her real power, but then the villain of the story is like "you can be free here, you can show them who you really are, I can teach you to use your full power", so she switches sides to unleash her real power.

All I could think of was X-Men hahaha but I would love to read some books where this happens bc I don't remember the last time I read something like this, so, could you please help me find books that fit this?