Star Wars' newly-announced TV show, Star Wars: Tales of the Underworld, will include a showdown that will settle once and for all who is the better master: Star Wars' most powerful Sith, although it would be difficult for one to argue that Dooku was really equivalent in of raw power compared to Vader. After all, Anakin Skywalker defeated Dooku even before he had fallen to the dark side.
That doesn't necessarily equate to which Sith would be a better master, however, and based on Star Wars' next animated TV show, Tales of the Underworld, we may be getting the answer to exactly that question. Tales of the Underworld, which will premiere on Disney+ on May 4, 2025, will feature former Sith assassin Asajj Ventress. Based on one showdown Ventress is already confirmed to have in the show, new light will be shed upon whether it was really Count Dooku or Darth Vader who was the better teacher.
Asajj Ventress Was Trained By Dooku, While Vader Trained The Inquisitors
This Will Showcase What Each Learned From Their Respective Masters
The trailer for Tales of the Underworld shows Asajj Ventress going toe-to-toe with one of Jedi survivors of Order 66 and any other Force-sensitive beings during the Dark Times. This will be fascinating to see because Ventress is a brilliant duelist—as are the Inquisitors—but this is particularly exciting because it will mean a showdown between Dooku's former apprentice and Vader's Inquisitor.

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Although they ultimately had a massive falling out (to say the least), Ventress trained directly under Count Dooku for years, as was shown throughout Star Wars: The Clone Wars. The Inquisitors have been trained and led by Darth Vader himself, which has likewise been shown in Star Wars projects like Star Wars: Tales of the Empire and Obi-Wan Kenobi. Tales of the Underworld will therefore be a showdown between someone who was trained by Dooku and someone who was trained by Vader, proving who was the better master.
Tales of the Underworld will therefore be a showdown between someone who was trained by Dooku and someone who was trained by Vader, proving who was the better master.
Dooku Trained Ventress As An Apprentice, But Vader Didn't Care Much About The Inquisitors
The Truth Is, Ventress Has A Major Advantage
It will undoubtedly be brilliant to see this fight go down, but, while Vader was arguably the much more powerful Sith, it's likely Dooku's apprentice will come out victorious in this battle. This primarily comes down to the extent of investment each Sith had in their respective underlings. That is, although Dooku eventually abandoned Ventress, he was at first considerably more invested in her, viewing her as a true apprentice.
By contrast, Vader had no real investment in the Inquisitors. He saw them primarily as a means to an end, and he wasn't exactly dedicating time and attention to their training in the same way. There's also a question of how Ventress' skills may have developed since then, especially given she now seems to be on the light side of the Force once more. It will be fascinating to see who proves to be the better master, Count Dooku or Darth Vader, but, no matter who wins, Tales of the Underworld will be a thrilling new addition to Star Wars.