Champion ABILITY concept.

While this may be a bit of a specific counter to some champions, I think that an ability, which turns healing into damage. Basically, what i'm trying to say, is that lets say an Ashe has 100 AD and 10% lifesteal. She attacks somebody without any armor. it would usually heal her for 10. Instead, she would now TAKE 10 damage. Soraka, instead of healing her allies, will cause them to take damage. The spell would have to be cast on the person healing. So if soraka was healing said ashe, it would be cast on soraka. Thoughts?