I don't believe that Revan is the most powerful Jedi or Sith. I believe that he is the weakest, most pathetic Jedi or Sith ever.
Reasons why Revan is weak:
1. He didn't sense Malak's betrayal.
2. He made Malak died, if he didn't go turn to the Dark Side this would have never happened.
3. He was easily captured by Bastila and the Jedi.
4. He lost his memory.
5. He caused many death and pain from turning to the Dark Side.
6. He gave no mercy to Mandalore the Ultimate.
7. He can easily be defeated by the duelist on Taris unless he regains his strength.
8. He couldn't easily persuade Juhani to turn back to the Light Side, if he was a master of persuasion, he could have done that quickly, but he couldn't.
I mentioned some of those before. Revan may be totally awesome, but think of some reasons to bring him down and crush him. I really like saying how the strongest can be the weakest at the same time.
There is no emotion; there is peace.
There is no ignorance; there is knowledge.
There is no passion; there is serenity.
There is no death; there is the Force.