Revan and Malak were considered the greatest Jedi of their era, but that accolade was given to them during the Mandalorean Wars. At that time, Malak would have definitely been General Surik's superior in combat.
But after the Mass Shadow Generator went off, a lot happened to the Exile.
Her force bonds with Kreia and others allowed her to learn light-saber styles very quickly and become powerful in the force.
Visas Marr was able to survive Nihilus force drain and she soloed against all of the Exile's companions when she attacked the Ebon Hawk. The Exile managed to defeat her without using a lightsaber (Wookiepedia claims otherwise, but I don't think you can use a lightsaber until later in the game).
She was able to hold-off Sion on Korriban, a dark side nexus. And she was able to give him his final death on Malachor, an even more powerful dark side nexus.
Her force bonds were strong enough that her companions were able to resist Nihilus' passive force drain. Her struggling in the saber fight against Nihilus after the failed active force drain is IMO a feat for how good of a duelist Nihilus is rather than a low-showing for the Exile.
On Malachor, the Exile's companions were soloed by Traya and captured. The Exile managed to fight through the Sith academy by herself, rescue her friends, and then solo Darth Traya.
According to Kreia, the Exile was very charismatic. The Jedi counsel even claimed that she dominated the minds of the people she created force bonds with (which may or may not be true, the Exile's companions deny it, but there is a cutscene with Atton near the beginning that provides evidence that this may actually be true, so it's ambiguous).
The Exile was also able to teach her companions the ways of the force and turn them into Jedi. Revan created a mess in the galaxy and the Exile cleaned it up. In my book, the Exile had possibly surpassed even Revan by the end of KotOR 2.
Anyways, her beating the Sith Triumvirate is more impressive to me than Malak putting up a good fight against Revan.