I spent some time looking for tags for corruption or corrupted heroines (personal fetish of mine kthx), but I couldn't find anything. "Transformation" is a little ambiguous.

Dragonzordasaurus said:
I spent some time looking for tags for corruption or corrupted heroines (personal fetish of mine kthx), but I couldn't find anything.

dark_persona is probably what you're looking for.

Corruption is a little hard to find in a picture, though I must thank Mr GT.