Anikan vs Darth Vader. Anakin. Darth vader would lose very easily(as you can clearly see in the movies) The suit is heavy for him.
Obi Wan vs Mace Windu. Obi Wan, Mace may be strong in the force but his saber skills are poor.
Yoda vs Darth Vader. Depends if it's Darth Vader with the suit or the one just before the Mustafar duel. With the suit: Yoda, without: Vader.
Anikan and Obi Won vs Darth Sidious. Sidious, the emporer defeated yoda, Mace windu and atleast four other jedi with the one lightsaber.
Obi Won vs Ben Kenobi. Obi wan, I would say Ben because he has had more experience, but he is old and not as able as his younger self.
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