The Balrog vs The Witch King

Originally Posted by Morthoron

. . . so if a Balrog was as powerful as Sauron, why then was there no confrontation?

Because Sauron dared not try to evict the Balrog from his realm, no more than he did not with Shelob. The lesson of caution is well learned. The Balrog itself was not created with a view to dominate the world as a leader, but as a servant subdued to the will of Morgoth alone. I would compare this to the Witch King, soley commanded by the will of Sauron. Also, how many top draw powerful baddies could Tolkein accommodate in the LOTR as main characters? Certainly not both the Witch King and the Balrog, in addition to Sauron?