Mesmer
Not out of the goodness of your heart. But because the wahwahwah is pissing me off.
Also, there's the risk he'll just hurt anyone he comes across. I think stopping him now before he hurts someone I actually care about would be better. This way I deal with him with a clear head, rather than just go out and kill him, bringing that crazy demon bitch, and other people from this world down on our heads. Because if he even so much as touches Kenzi, I will end him.