He's powerful and probably more powerful then Sion was during the Kotor era. However Sion lived for a lot longer then Bandon and you know the control over the force he should have, he's an assassin and probably a great fighter too. I don't know if he can outfight Bandon but I think so. At least it seems like he has the force power to do so. And the skills with a lightsaber, even an assassin has to fight.
Sion can probably put up a good fight against Bandon, I don't doubt that. I haven't seen anything to indicate Sion is a better duellist (actually, he's an assassin. His forte is stealth kills and ambushes, not outright combat like Bandon) But with his invulnerability definately tips this in his favor.
I don't think Bandon has the force powers to drain the force from Sion. He won't be able to destoy his will either... Meaning that he probably can not kill Sion.
And I realise Sion is an assassin but also a Sith.. I don't know how they killed other people you probably know better then me, seeing as you've played Kotor II a billion times. But assassinations can still be fought in straight out fights. Or it can be done by trickery, I don't know which Sion used, but if he didn't fight head on then those 5 extra years will hardly mean anything and Bandon will still take him, just not able to kill him and he will have to run at some point.
Well, there isn't an instance of Sion fighting any saber user in direct combat other than the Exile, and I think that was more of a pride issue than his usual routine. For instance, Sion played dead and had his assassins cloak so they could infilitrate the Harbinger. Later on, Sion's forces frequently employ stealth tactics that ninjas would envy. And of course, the fight with Kreia was a one-hit wonder. Sion has his back turned, pretending he can't see her, then suddenly whips around and takes her hand off. But still, that fight bothers me. How did she escape? Why did he let her go? Why did he not kill her? Was it all a plot to allow the Exile to lead them to the jedi?
Well okay, Sion probably isn't that great of a fighter, you have convinced me of that.
And about him not killing Kreia I never got that either.
I can think of a few possibility's though
1.) He let her go, its obvious Sion loves her even as he hates her, he could not bring himself to kill her or perhaps didn't even want to. You have to remember he let her go once before, why would he have done that? Perhaps he wasn't allowed to kill her perhaps Nihilus needed her, or perhaps he was just unable to do so because of his love for her. Whatever the case he let her go out of fear or love.
2.) Kreia simply knocked him out after he took her hand, of course that would be a possibility knowing Kreia and her power, but that wouldn't explain the other time he let her go. And why would she keep Sion alive? She never intended him to face the Exile for as far as I know, at least she never has him face the Exile up until Nihilus. Then again she could have taken him out on Korriban but didn't. It seems to suggest that she had a reason for him to be alive. On the other hand she may just not have killed him to make sure the Exile wouldn't know of her far greater powers.
Okay, so I just thought of this while typing tihs reply, I can probably get a better answer when I think about it longer, but I think it can stand for now. Theory's start small after all 😛
That still keeps the question around.. Why is Sion important? Sion being important to Kreia after Nihilus okay. But at first she would have assumed there would be no threat after Nihilus what happened there was not what she had hoped for. So Sion could have been a safety net in case things went wrong and the Exile went to face her. But when the Exile came she didn't even put up a real fight. She didn't even fight him to the death because she wasn't prepared to do so.
So the question still remains, what was Sion his goal? Maybe he was a safety net that she decided to remove because she had a change of heart but whatever the case her reasons for keeping him around just seem vague.