And posted!

[@thewizardguy] And yes, there are more powerful sith lords out there. 

*Begins to slowly polish his old rusty Star Wars nerdieism*

Starkiller isn't the strongest either. But to be fair, some even speculate that the powers we see him commit is not exactly his true potential. Hell, even Palpatine once said that he could've one day been his equal. There's a video down below that describes Marek's power against that of Revans. Yes Revan will win due to his more advanced force powers and balance of light and dark sides, but its pretty close. Given if Marek improved on his powers some more, (i.e: Trained longer or survived Palpatine's), he could be at least on par with Revan if not more. 

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[youtube]https://www.youtube.com/watch?v=BbNjC71-KV4[/youtube]
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But again, you are indeed right for him not being THE most powerful sith/jedi, but he's at the most part a notable and popular force figure.