Weren't they herded into some temple and bombed though? Even if not he lived by chance, there were powerful Sith there. So he gets lucky once and he's strong enough to take on somebody that is viewed as simple power? Doubt it.
Revan didn't really bring back the Sith at all. Kun brought them back, and after they were defeated it not Revan then somebody else would have. There was a Sith academy on Malachor ffs. Somebody was bound to find that.
Revan was powerful, but you never got to see any of that potential at all. They made Revan character defined as calculating and genius (Sentinal) powerful in the force (Consular) and an unbelievable duelist (Guardian) Guess why Revan got that description? I'd say the Exile is better even though I don't really like the Exile much, but Exile's potential goes to killing entire planets with little effort.
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Actually they were battling the jedi on an open field. Him surviving was no chance, he was obviously the strongest of the sith lords present there.
Maybe Bane is not stronger than Revan but he is not under him on terms of power.