I'm just throwing suggestions out there, names and actual attributes are up to whoever decides if they should go in. The reason why I suggested "Eye for an Eye" do 2.5 times damage is that enemies health pools tend to be much larger than player's health pools, but I suppose it doesn't matter, taking the same amount of damage as they deal out is still damage that wouldn't be happening without the curse.
The idea that the witch would also take damage if they attack the one who is cursed is interesting, but that would not be great for melee-class characters who would otherwise use it. I don't think it needs such a downside.
I was... joking.
Eye for an eye expression is more or less explicitly referring for reciprocal same amounts of retribution... so saying it would cause 2.5 amounts of damage... translated back would mean... ? more eyes and peckers, noses, ears - haha?
humor, yahwoll?
The version of the curse is also meant to be a funny, tongue in cheek and a sarcastic skill, (which would almost fit general Larian style, btw)