[Suzerain of Sheol]

Well, you know how Tolkien experts are, they can write in-depth essays on any aspect of the books. :p

And, yeah, but you have to weigh any potential candidates against the acts of fate that allow Merry and Pippin to contribute to the war effort against Sauron. I think Glorfindel is powerful enough that his aid outweighs anything they did, unless he was got deployed to fend off Sauron's northern armies or something.