Star Wars Question

So there's the whole Rule of Two for the SIth thing that means the only Sith about during the original trilogy was Vader and the Emperor but it as been established that there was a whole host of Dark Side Adepts and Apprentices during that time so I was wondering has it ever been mentioned who was the most powerful? Is it Starkiller or are there others?

It has never been stated explicitly as there were numerous Darksider adepts as you said, but it can be implied that Starkiller is among the most powerful ,possibly the most powerful.

@makashi1023: do you know of other notable ones?

@jonny_anonymous Darth Malak was Revan's apprentice. Technically though, Sidious was the most powerful Sith apprentice that ever lived.

@juiceboks: Yea but what I was meaning was other than Vader and Sidious who were the most powerful darksiders at that time.