As it's already been stated, Luke and Ragnos are pretty much equal as far as we can tell, though it's a little shady as all the info on Ragnos is conjecture and assumptions. Still, I think they'd make good opponents for each other.
How much of "the most powerful of the most powerful" is conjecture? We know he was not just good, but purely dominant. We know no one dared to attack him on his death bed. We know that Ludo Kressh submitted to him as "the Dark Lord" after he came from the dead, we know the Naga Sadow, Ludo Kressh, Exar Kun, and Ulic Qel-Droma all stopped their fighting and submitted to his will. He is described repeatedly as a godlike and terrible foe. He "dominated" over other ancient Sith that could make the Jedi of Revan's time look like children with lightsabers. He ruled unquestioned and with an iron fist over a wealthy Empire for over a hundred years -- an empire where the strong rules. He put "the most powerful Sith Magician of his time"'s head in a jar and still decided to keep him around. His passing into the Dark Side was so powerful, Odan-Urr felt it all the way in REPUBLIC SPACE. From other EU sources, he has a scepter that can drain the force from entire PLANETS even in the hands of a relative weakling like Tavion. It can imbue non-force sensitives with force powers and lightsaber abilities. It can cut through buildings with ease.
Don't tell me that all we know is conjecture and assumptions. Use your brain a bit and you'd see that every single of his descriptions is one of absolute titanic power.
I love the logical fallacy of people around here. We have all the logic and evidence suggesting Ragnos was some uber lord over the Dark Side, yet somehow, someway, using some paragon of twisted logic, they assume the very worse out of him. What low showing are you going off of? His defeat to Jaden? His 5000 year old spirit's defeat to Jaden when he possessed a body that was already beaten? His defeat that didn't even kill him?
Funny, truly funny.
How is Luke equal? Because he fired "green lightning"? Because he was shown in the movies? Because he controlled a black hole (a feat duplicated by one of his OWN TIME)? Because he slashed through some Vong?
I'd personally bet on Ragnos do slash through those same Vong, particularly since he is renowned for "immense physical strength and a frightening grasp of the force." And I'd rather face Vong than 20 Sith Lords who were described as "godlike" entities with "titanic" power.
Now, Kun vs Sids is very much the same. I'm going to give Kun the benefit of the doubt and say he could win, albeit with some difficulty, in saber to saber combat, especially considering that Sids lost to DE Luke, though that may have been after Luke's power was augmented, which would only help him. Still, Sids has the single most impressive show of force lightning in the history of it's use, not to mention the draining of the people of Byss.
By that same notion, JA Luke, which is after DE Luke, said they would need the entirety of the Jedi Academy's forces to stop Ragnos if he were ressurected. By game mechanics of JK:A, if you beat Tavion the first time, you officially (canonical wording) "thwarted" her plans of ressurecting Ragnos.
Ergo? Ragnos never manifested, he simply had his spirit possess a weakling of a body and likely assumed all the limitations. And yet? The body suddenly had a huge force power augmentation and had a speed bonus you wouldn't believe.
And Kun? The guy who tore holes in temple walls just by blasting them? The guy who froze the entire Senate and casually waltzed his way in? The guy who tossed Sylvar with such ease that it was almost comical? The guy who broke through Vodo's staff that was "stronger than a lightsaber" according to the omniscient narrator? The guy who destroyed a 400 year old spirit that had the ability to instakill other force users? The guy who stockpiled so many secrets of the sith that he could never even use it all? The guy who was practically crowned by "the Dark Lord of the Sith" as the second coming of the Golden Age? The guy that single-handedly required the largest collection of Jedi in history to simultaneously converge on his base of operations?
Yeah, that guy. What logical evidence do you have for Sidious? Force storm? What about the blasts that Exar casted repeatedly that shredded an ancient Sith Alchemical Creature?
Can force storm be focused on a single opponent? Can he use it without taking out the battlefield? Can he do it while Kun brings his double-bladed lightsaber down on him? If he can't, it's not within the rules. And the draining of the planet is hardly so impressive when we see Tavion doing the same thing to a number of planets with the scepter. I personally think what Zonama Sekot and Nihilus did were far more impressive.
1. And Mandalore was only the head of a warrior sect who've been known to kill Jedi. By that logic, nothing special about Revan
Except that he also walked into the Star Forge and beat down a Jedi renowned for his battle prowess WHILE he was boosted by the power of the Starforge.
2. which begs the question: How did Ulic use that amulet in DlotS? How did Exar not blow Ulic away from the start? Or Aleema for that matter?
How does this retort to his point?
Oh wait, it doesn't. It's irrelevant misdirection and logical fallacy. You're arguing with what's literally portrayed and is shown and direct inductive observations from the text.
A better question would be if Sidious had "discovered the darkest secrets" of the Sith, how come he didn't use the artifacts and other paraphenelia? He'd be stupid to not use stuff that boosted his power. Ergo, he either a) doesn't have them, b) is retarded, or c) the DE Sourcebook is outdated and has been shown redundant (e.g. mentioning the Sith Order as 2000 years old instead of the 5000+ that it really is like in later canon.)
5. Proof spirits are weaker than flesh and blood? Unlike Obi-wan, Exar had the power of the Massassi, not to mention a place that was a focal point of his power
The proof is in Obi-Wan. He's stated a fact. Spirits like Obi-Wan and Anakin get weaker over time and are no longer able to influence and visit the living.
Law of debates tells me you have to disprove this. If he was stronger in death than life, how come he didn't use blasts that he did in life? How come he didn't use the instakill attacks he's SHOWN to have? Logic dictates he isn't stronger. You arguing against first order logic shows you're a fanboy.
6. Right, because amulets and artifacts are as part of someone as arms and legs...
STFU.
Did you not read the first post? Artifacts are perfectly legal in this fight.
Tell me, place Kun's power EXACTLY with the artifacts and show observed evidence for this. Show me where it says something to the effect that "an amulet increases force power exponentially" or something like that. I'm confident you won't find something to that effect, why? BECAUSE I READ THE COMICS.
So stop griping about amulet this, artifact that. The listed parameters are already in the first post. You trying to change them is simply trying to load the die so Sidious and Luke wins.
Guess what?
Feat wars don't make someone win. By that logic, because Sidious never created superweapons with the force, he's not anywhere near as powerful as Naga Sadow. Or because he didn't rule UNQUESTIONED, and was never dethroned, over an Empire of Sith under their "golden age" he'll never touch Ragnos.
Same concept. Silly conclusions.