Only Sith I know are Darths Vader, Sidious, Tyrannus, and Maul.
Of those four, Obi-Wan beat Vader and Maul. Tyrannus beat Obi-Wan but Yoda spanked Tyrannus. Sidious and Yoda were fairly evenly matched. Suggests that Sidious was strongest of that bunch, but since I don't know the other six, I'll abstain.
English
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Sidious is one of the weakest of the list. As revan mastered both the light and the dark