I'd like to point out that it's highly inaccurate to say that either Exar Kun or Naga Sadow, with their own power, ripped the cores from stars.
They did this using a blend of Sith magic and technology. The only way they could do it was by using Naga Sadow's ship, the "star-ripping" was its primary weapon that only a Force user could use. Why do you think Exar Kun sent Aleema, by all respects a very low-level Force user considering he knocked her out in one blast before becoming "Uber-Kun," to destroy the Cron Cluster and thereby destroy Ossus?
That means, technically, Aleema Keto "ripped the core from a star." That doesn't make her powerful, since she used Sadow's ship to do it, as did Sadow himself.
Moving on, the ability to kill a Jedi with a blaster isn't too impressive. Does anyone remember Coleman Trebor getting blasted by Jango Fett? Any number of scenarios could arise where Nadd could use trickery to blast a Jedi. I envision him dueling with his lightsaber and then blasting the Jedi from point blank range, for example. (This is despite the fact that I think KOTOR is irrelevant to arguing EU Star Wars, since it contradicts other sound sources and also plays "hard and loose" with the facts for the purposes of putting together a game that is fun and will sell well.)
However, Glentract, I do remember his "bombs and poison gas" advice. HK-47 gave the same advice in-game.
And again, I don't think Nadd conquered Onderon. I think he merely used a less subtle Sidious-like political maneuvering and dark side powers to put himself in power. Sure he fought the beast riders, but since they were at a constant war with the other people of Onderon that doesn't make him special. Honestly I could be wrong, but from what I remember of my TOTJ, he didn't stand against the combined might of all the peoples of Onderon and win. TOTJ: Dark Lords of the Sith says, "Nadd roamed the uncharted (backwater) systems, until he found a world (Onderon) he could dominate (emphasis theirs) using the powers of the Dark Side."
Oh, by the way... I also don't think Naga Sadow was ever the Dark Lord of the Sith. According to the holocron Exar Kun is studying in the beginning of Dark Lords of the Sith, when Naga Sadow fled the galaxy, he was
exiled by his Dark Lord, branded a criminal by the Republic.
Just a couple of pages later, it says that Sadow
vanished with his followers (to Yavin Four). Sadow was a member of an elite priesthood, of pure Sith blood, who were in rebellion against their Rulers, the fallen Jedi who wore the title Dark Lords of the Sith
If the holocron is true (as well it should be, since it was a history Vodo Siosk-Bass was keeping) then the KOTOR nonsense about Sadow ever vying for the throne of Dark Lord is nowhere near true, much less the even bigger nonsense about his tomb being on Korriban.