Well, I suppose Galadriel could always dig Radagast up, since he lives nearby, then put the fear of, well, herself on him to do his darndest...
The Balrog WOULD be worn out from Gandalf-fighting, but I still wouldn't put his chances of being taken down too high. This is, after all, Radagast...
Still, he would be that much more worn down that Celeborn and a long string of archers (if necessary) could be sent in to finish him off, suicide Glorfindel/Ecthelion style...
All they need is a rock and a high place.
