Revan was amazeballs in terms of physical and force power; I don't know for sure but didn't he defeat mandalore in one on one combat? Anyways he wasn't the most OP guy ever but he was a strategic mastermind, canderous gives revan like 24/7 praise for his crazy battle tactics that were impossible to counter. On top of that he was charismatic enough to take a huge chunk of the Jedi to fight with him in a war the Jedi specifically forbade.
Idk much about the 100% canon version but my interpretation was that he was amazing with his use of the force but only decent (in Sith Lord standards) with the lightsaber. However, his strategic mind was unstoppable (basically him normal battle was roughly equal to Bastila battle meditating everyone) and he was crazy charismatic. Meanwhile malak was alright with the force (again, by Sith Lord standards) and Was an intense, darth Vader like, lightsaber user.
I never played TOR or read the comics or whatever they had so I don't know all about him, but it's well stated in both KOTORs that he was a military mastermind. And we also know that he was far better than malak in arguably everything.
TL;DR yeah he was OP, but what Sith Lord wasn't, his real strength was his military tactics and charisma.