Exar Kun vs. Darth Malgus

Who wins?  Within the next few days I will be making an analysis on how a fight between these 2 would go down.

1.  Sabers
2.  Force
3.  All-out

Well, here's my analysis on these character's respective arsenals:
 
Sabers
 
Exar Kun was a prodigy of the lightsaber, said to have "unparalleled lightsaber skills," while a mere padawan.  He's defeated Vodo Siosk Baas (twice), a jedi guardian who has 400 years of experience to hone his lightsaber ability.  He's stalemated Ulic Qel Droma, who has very impressive saber feats and was considered one of the most powerful sith lords in history, as well as the greatest warrior the jedi order had.  He was the ultimate master of Niman, using a more aggressive form to suit his headstrong nature.  Kun also has a unique saberstaff hilt, which he can change the length of at a whim to confuse his opponents.
 
Darth Malgus was also a master lightsaber duelist, and when giving into rage, a nearly unstoppable foe.  He displayed his prowess when he defeat Kao Cen Darach, the Jedi Order's Battlemaster, while just a sith apprentice.  Around 30 years later, he lead the Sacking of Coruscant and killed Ven Zallow, the jedi master tasked with defending the jedi temple, in an epic duel. Malgus specializes in Djem So, a lightsaber form predicated on brute strength, which works well with Malgus's attributes.

Verdict:  Exar Kun is an incredibly aggressive lightsaber duelist, with a unique lightsaber hilt.  However Malgus is the more physically imposing of the two, and his brute strength would serve as an advantage.  So now we must look to their feats.  while both have defeated jedi weaponsmasters, Exar Kun's stalemate of Ulic Qel Droma is, imo, more impressive than Malgus's feat of beating Zallow in a good fight.  Ulic Qel Droma has defeated a mandalore while severely disadvantaged, stalemated a jedi knight (Sylvar) while having literally no connection to the force, and was one of the most powerful sith lords in history.  Zallow, while an impressive duelist in his own rights, doesn't have the feats or the accolades to match Droma.  Exar Kun gets a very slight edge as a lightsaber duelist.

The Force:

Exar Kun was an immensely powerful force user.  Learning at the feet of Freedon Nadd, it was extremely likely that Kun knew how to utilize illusions.  Kun, as a force spirit, was capable of choking out a dozen jedi with telekinesis. He's frozen the entire senate, and killed Odan Urr with a mysterious force power (assumedly TK).  But most powerful of all were Kun's amulet blasts.  These blasts could one shot an enormous sith wyrm, blasts huge holes in stone walls, and one shot Aleema Keto with negligible ease.  These potent blasts were very arcane and few expect anyone to possess such an ability.  Also to note is that Kun has accolades noting him as, "the darkest power in the galaxy," as well as the most powerful sith lord who ever lived.

Malgus was also very strong in this force.  His TK has destroyed columns in the sith temple, blasted Zallow and Aryn Leneer, etc.  His lightning has destroyed jedi and completely overwhelmed Aryn Leneer after his epiphany.  His raw power was great, as his force scream was powerful enough to destroy fighters by overloading their fuel slugs.  He also displayed the ability force maelstrom, which was a powerful combination of a force bubble, lightning, and TK.  The only beings who knew this ability were Malgus, Galen Marek, and Darth Sidious himself.

Verdict:  While Malgus's raw power is arguably greater, Exar Kun's superior mastery of the force as well as his amulet blasts provide a significant edge, meanwhile Malgus's lightning and TK most likely won't be strong enough to overwhelm Kun.  However, Malgus's force maelstrom would prove to be an incredibly useful weapon, so Kun wouldn't stomp Malgus in this regard.

Conclusion:  While Malgus is certainly skilled and powerful in his own right, Exar has slightly better feats as a duelist, and is much more learned in the ways of sith magics and alchemies.  I declare Exar Kun the ultimate victor.