I'm guessing it's a toss-up between Muur and Pall right?
__________________ "Vader's pulse and breathing were machine-regulated, so they could not quicken; but something in his chest became more electric around his meetings with the Emperor; he could not say how. A feeling of fullness, of power, of dark and demon mastery -- of secret lusts, unrestrained passion, wild submission -- all these things were in Vader's heart as he neared his Emperor. These things and more."
Pall was the leader. I'd imagine if Muur was his equal or superior, he'd have challenged him.
__________________ There's a man goin' 'round takin' names.
An' he decides who to free and who to blame.
Everybody won't be treated all the same.
There'll be a golden ladder reaching down.
When the man comes around.
__________________ "Vader's pulse and breathing were machine-regulated, so they could not quicken; but something in his chest became more electric around his meetings with the Emperor; he could not say how. A feeling of fullness, of power, of dark and demon mastery -- of secret lusts, unrestrained passion, wild submission -- all these things were in Vader's heart as he neared his Emperor. These things and more."
The Exiles showed more power than most of the sith lords in the mythos.
__________________ There's a man goin' 'round takin' names.
An' he decides who to free and who to blame.
Everybody won't be treated all the same.
There'll be a golden ladder reaching down.
When the man comes around.
"The five nigh-godlike sith of legendary power, who fought the Jedi to a standstill for a century! ... oh, and these other people. Here, here's the first of the 'and they were there too's."