Gandalf Vs. The Witch King

All you have to do is read JRR Tolkien's book......Gandalf learns of Theodens death
It quotes: Shall we weep or be glad? Beyond hope the Captin of our foes has been destroyed, and you have heard the echo of his last despair. But he has not gone without woe or bitter loss. And that I might have averted but for the madness of Denethor.
Gandalf is an Marai exactly the same as Sauron himself but is not permited to use all of his power which was part of the bargin of the chossen wizards coming to middle earth.
He is without question more powerful than the witch king....But all would know this if they really read the book and not just take what they want from words within and creat their own meanings