Regina's magic did come from a place of hate and revenge, but it does not have to be that way. In part, it is how the magic is used by the one who wields it. However, all magic comes with a price in our world. I have yet to know how that transfers to this world, but where we come from, magic always had its price. Of course, the good magic never had a dire price. It is mostly the dark magic that had those kinds of consequences.
Magic can be tied to emotions, and it can change a person when it is used. It can become an addiction the more it is used. It was that way with Regina when she had it in our world.