Did I say anything about those spirits? He just released the energy, and considering the narraration says that's what he did...
When does physical strength mean anything when the force is concerned? This's recalling this is a younger non-Sith Kun not expecting Nadd to yank the saber away...was Kun even using it when Nadd grabbed it? I'll have to reread that scene.
So some dialogue was exchanged...Matta's a moron one way or the other, this was obvious...there's nothing that indicates a duel took place. It says she refused to promote him and he lashed out. He goes to the Jedi Masters, they refuse him, so he goes to seek Matta out, where she tells him he can't be a Jedi and that some things he must find in himself. He screams at her, she doesn't tell him what he's lacking and he attacks, whereupon she leaves herself open. He kills her, sees what he's done and flees.
What? Tarkin was in complete control of the death Star. And that's two personal losses for Vader...the base on Hoth was totally wiped out and the imperials gained a voice on Cloud City for several years. And that's two battles out of many others Vader was involved in. And yes, the Rebellion was losing the war. Their numbers were severely depleted and some systems had defected back to the Empire.
Okay, stop this BS about Nadd continuously exiling people, because there's nothing backing it up. In fact, it just says wuite a time later after he kept exiling people they came back in force, so noone knew what was going on until this guerilla war happened. If you have a source of Nadd exiling criminals AFTER the guerilla war started, this point might hold some weight. In fact, it states the policy totally backfired on him.
And Sith spirits clearly have some ability given that they possess human form...Kun certainly didn't suck in his spirit form as he showed Gantoris and Corran Horn. And Ommin blasted Nomi and Ulic. Ulic charged right through it.
On Ossus? Once again, you'd have to tell me WHERE this confrontation took place on Ossus and what happened...Nadd was so horrified, he immediately fled. Seems sound there were no other Jedi around.
Nadd has one place of power on Onderon and even if the Beast Riders' strategy is 'hit and run', Nadd and his forces should be able to deal with it.
The only Massassi who took down a Jedi that we saw was kilgrath, AKA The Night Beast, AKA alchemically altered by Exar personally. Moreover, can you prove Nadd didn't poison Sadow or that the Massassi were even around? Likely Nadd lashed out at him impulsively when Sadow refused to teach him further.
The faith of an entire planet? Last I checked, Onderon was stuck in a civil war against the Naddists for four hundred years. Point made on the issue, though there are some attempts to beef up Nadd quite a bit.