I think I just came up with another way Revan could "cheat" his way to defeat Nihlius. Prehaps, it might be considered a pretty legit method.
Revan, being a smart being, would know that Nihlius has his Force Drain ability, and knows that Nihlius would beat him in a fair fight. So, Revan withdraws to what is really his strength: being a stragisit. Sure, we don't know how good a general he is, but he won the Battle of Malachor V, so whatever his methods, it works.
Revan has a great mentor named Kreia who taught him all he knew, and then some. Revan would have realized that Nihlius is consumed by his hunger, that he will do whatever it takes to sastify his hunger, and the more powerful he is, the stronger his hunger becomes, until all life in the galaxy is destroyed.
So, I assume Revan would just run. He would do whatever it takes to misdirect Nihlius, send him to destroy worlds that have no Force Senstivies at all, that have no Jedi at all. Nihlius would waste time, and energy defeating these worlds, searching for Revan. Revan would send in strike teams, knowing that they would die, but it will act as a distraction to Nihilus, and distractions are key. The more time Revan can bide, the more time his hunger can work against Nihlius. If Revan gets lucky, Nihlius will finally starve to death. And Revan wins.
Kreia said about Nihlius that he is already dead, that the only thing that matters is how many worlds he eats before he falls. Kreia believed that if he isn't stopped now, he may become impossible to stop in the future, and all that one can do is avoid Nhilus and run, waiting for Nihlius to die of hunger, like Revan possibly would have done.
[Kreia actually hoped the Exile wouldn't have to fight him, worried that the Exile will lose, and hopes that the Exile would be prepared to kill off Visas to weaken him... (How ironic that Kreia feels this fear...since the Exile is a wound in the Force, meaning that he's the only one that can kill off Nihlius. Of course, knowing Kreia, I'll assume that "mistake" is just another Kreia Lie).]