Revan is "far more powerful" than Darth Nihilus
1.) Revan, as of the Battle of Malachor V since that was the last time Meetra Surik has ever seen Revan, was more powerful than anyone else she had ever met, meaning he is more powerful than Darth Nihilus:
"It was easy to understand how Scourge could be drawn to him; Revan's command of the Force was greater then that of anyone else she had ever met."
2.) Meetra Surik was in complete and utter awe over Darth Nihilus' destructive capabilities:
"To kill on such a scale... it's impossible. I don't understand - it would have taken several Republic cruisers to destroy the surface of Katarr."
3.) Meetra Surik found Darth Nihilus to be "far more powerful" than she had originally believed above when she confronted him:
"He speaks, his voice roaring, and the player should realize that Nihilus is far more powerful than they had believed."
4.) Revan had become "far more powerful" than the last time Meetra Surik had seen him:
"Revan had grown since then. He was far more powerful now."
5.) I found examples in Star Wars literature where Drew Karpshyn uses "command of the Force" to describe one's connection to the Force / raw power:
"Without proper training, even his enormous command of the Force was unable to anticipate the unfamiliar sequences of the two-handed fighting style."
"The lightsaber was an extension of the user and his or her command of the Force."
"But his command of the dark side was too powerful for it to hold him for more than a split second."
6.) In particular, this passage makes an explicit link between power and command of the Force:
"Was it possible there was some other essential element in the process that he was missing? Was there one more secret waiting to be unlocked that would finally allow him to create a Holocron so he could pass his wisdom and knowledge on to his successors? Or was the failure in him? Did he simply lack power? Was his command of the dark side somehow less than that of the ancient Sith Lords like Freedon Nadd?"
7.) Also in other works, we see "command of the Force" as a synonym for one's potential / raw power:
"Sometimes he felt there was so little he need to teach his Padawan. Even to Obi-Wan, who knew him so well, Anakin's command of the Force could be astonishing."
"His sensitivity was far from perfectly attuned and he sincerely doubted he would ever attain half the command of the Force that Kenobi had possessed? though the old man had expressed great confidence in Luke's potential. "
8.) Darth Malak was believed to may have eventually surpassed Darth Revan, meaning he also surpassed Darth Nihilus:
"When Revan fell we had hoped the Sith threat was ended. But Malak quickly assumed Revan's role, and has embraced the dark side power as fully as his old master ever did. Now Malak leads the Sith armada against the Republic. Hate and vengeance for his master's death draw Malak ever further down the path of the dark side, fueling his powers until they surpass those of his old master."