To be honest, it's hard for me to properly judge the power of individuals like Vitiate or Bane, given that there's a lot of "nexus" and "amped feats" controversy going on.
I'm also not sure where to place Nihilus, who on paper should be the most powerful, but his feats where questioned.
It's not exactly clear to what extened he was in control of his powers and not just a mindless force of nature. If he was just a tool, so to speak, that would preclude him from this list IMHO.
Well Nihilus was capable of creating a holocron (which RoT showed requires extreme concentration and care), as well as holding conversations and making conscious choices. He wasn't really a slathering beast, more like a junkie. Still a person, just with highly influenced behaviour.
So you think Revan > Luke and Sidious > Vitiate yet Revan was defeated by Vitiate and Sidious was defeated by Luke. So shouldn't it be Luke > Sidious > Vitiate > Revan? No offense but considering the rest of your list as well, I'm not sure if this is an actual list or an attempt to troll people.