Sidious vs. Plagieus
We all know the story of Darth Plagieus the Wise. He said Darth Bane's Rule of Two was no longer necessary, he became insanely powerful in the dark side, only to have Sidious kill him in his sleep. If Plagieus and Sidious were to have a full battle in the way the Rule of Two dictates, who truly comes out on top as the most powerful Sith Lord ever?