Let's go over this for the reading impaired...
Freedan Nadd- Killed his jedi master embracing the dark side.
Juhani- Nearly killed her master embracing the dark side. As a mere padwan, she controlled beasts and corrupted a portion of Dantooine's grove.
Exar Kun- embraced the dark side, obliterated Nadd's spirit, a Sith wyrm, cowed all the force using massassi and WTFpwned Odan Urr and Vodo, while making Sylvar his *****.
Ulic- embraced the dark side and became pretty uber (Though he was already pretty uber).
Malak- embraced the dark side. Casually force pwns jedi with ease.
Dooku- embraced the dark side. Could more or less stalemate Yoda without being overcome. Could take out Anakin and Obi-Wan at the same time.
Skidious- embraced the dark side. Could defeat Yoda in combat despite being far younger.
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Did you READ the material?
Nadd killed a master in a sparring accident.
Juhani: The entire thing was a test.
Exar Kun: Special case, still got pwned at the end and later on, tricked by padawans.
Ulic: Miss the part where he got banned from the Force and went into a fit of crying and that whole exile thing?
Dooku: Knew he was going to lose. Ran away. That's a loss
You know what all of those guys have in common? The Jedi beat them at some point or another