Cade Skywalker's rejection of Darth Krayt's temptations not because he chooses the Light Side, but because power doesn't interest him. Krayt himself is pretty much baffled when Cade refuses to fall for the old “strike them down” bit.
Darth Krayt sitting upon the throne of the Emperor. By himself, Krayt has restored the galaxy to the Dark Times.
Topped when he comes back from the dead. Then he tops that by echoing Palpatine when he says that everything is preceding as he planned.
Darth Wyrrlok gives a Shut Up, Hannibal! to Darth Andeddu and then promptly slaughters him in a Dark Side duel, proving the One Sith are just as powerful as those who followed the Rule of Two.
Cade in issue #19 when he, after only about two months of Jedi/Sith training following seven years of disuse, takes on Krayt, Talon, and Nihl- and he defeats the Hands in seconds before battling Krayt to a standstill, all the while refusing the call of the Dark Side.
The Heroic Sacrifice of Captain Yorub when he kamikaze attacks the Mon Calamari shipyards and destroys a third of them, preventing the Sith Empire from creating anymore ships there.
Celeste Morne deserves props:
Kept Muur, one of the original Sith Lords, at bay despite being alone for the best part of 150 years, remaining entirely rational and in good physical shape by learning to tap into his powers to sustain herself.
Despite being well over a century out of practice, she demonstrates the same sabre prowess that led to her matching up favourably with Darth Vader himself, comfortably carving through each member of the One Sith that she faces, swatting aside Antares Draco, and manages to more than hold her own against Darth Krayt, an absolute juggernaut of a duellist, with Muur constantly attempting to take over, and finally setting him up for Azlyn Rae to strike him down.
Swiftly identifying both Cade's gifts and the fact that despite how close he is to the Dark Side, he has absolutely zero interest in power. She identifies him as the one other person who can not just resist Muur, but destroy his Talisman. After Cade gives her a Mercy Kill, and takes up the Talisman, he cuts off Muur's Evil Gloating by pointing that Celeste knew exactly what she was doing and that he can destroy the Talisman - which he does.
Related to the above, Cade resisting Muur's influence and shattering his talisman with Force energy while Muur can only scream in impotent rage. After watching Muur torture Celeste for 8 issues, seeing Cade banish the guy into oblivion as well as Muur's Villainous Breakdown was quite satisfying. Celeste picked her successor well.
Kol taking down around 10-20 Sith by himself before being struck down by Nihl to save Jedi younglings.
One for Krayt on Korriban in issue 5. After contacting the spirits of three Sith Lords (Bane, Nihilus, and Andeddu), they denounce him as a "pretender" due to uprooting the Rule of Two that Bane created, then use the Force to accelerate the growth of the Yuuzhan Vong organisms that are slowly killing Krayt. Cue him them spraying the organisms with Force Lightning to make them recede before denouncing the Lords around him, saying that if they won't help him, he'll find his own way.
One for the Jedi Healer Hosk Trey'lis. Wounded and hurt, having forgiven the Anti-Hero who turned him over to the Sith authorities, and knowing he is about to die at the hand of the greatest Sith of this era, what does he do? What is the single most devastating thing he can tell Darth Krayt?
