Darth Nihilus Vs Darth Sidious

This is complicated and the result depends on a few variables.

Nihilus has the power to strip Sidious in all 3 stages before Sidious can think after directly after Force draining Katarr.

Sidious could probably speed blitz Nihilus at other times, and DE Sidious is far more esoterically inclined than Nihilus ever was, but still no wound. He performed experiments with mass Force drain, he was a nexus of Dark Energies in ROTJ and DE, but still no wound so Nihilus still has the upperhand per Force drain. However, DE Sidious may have a few tricks up his sleeve. Sidious learned of Force drain during his tutelage as a Sith Lord under Plagueis, but it would be of little use. Sidious can take Nihilus out fastest as either a youthful clone or in ROTS, but he'd be best in TPM when his skills in combat were at their sharpest.

So, in summary, it depends on how much excess Force energy Nihilus has kept from his "feeding sessions", how much absorbed Force Nihilus has at his disposal, at the time of this battle. The same would be true for Vitiate.

Sidious would perhaps fair best after experimenting with Force drain on Byss, even if he is old and decrepit clone, he still has far more "stolen Force" at his disposal at that point in DE than at any other point in his life, and perhaps enough to make his physical stats go way up ensuring a speed blitz unless this is Nihilus right after Katarr.

All the Emperor needs to trigger a Force storm is "mere thought and inclination" (The Essential Guide to the Force).

More importantly, between Dooku's excavation of the Dark Reaper and Palpatine's own prodigious demonstrations of a Force drain, it's silly to think he's incapable of wielding it against a single opponent.

I think it comes down to who's quicker on the draw and it can be reasonably inferred that Palpatine's arsenal is much wider than Nihilus's. At worst, I think it's a stalemate.

Didn't Sidious instruct Dooku how to handle the Dark Reaper right before the latter did so?

It's implied by a Fact File but never outright confirmed. Though, again, the idea that Sidious would hand Dooku a superweapon of that magnitude without some form of protection or redress from the Count's treachery is... silly.

If Sidious can successfully defend himself from Drain, he's got it in the bag.

Dooku never expressed a desire to betray Sidious tho.

Sidious instructed Dooku to kill Ventress for exactly that reason though.

Originally posted by Nephthys
Dooku never expressed a desire to betray Sidious tho.

He emphatically expresses a desire to betray Sidious in the Clone Wars episode "Monster."

And Dave Filoni confirmed it before the release of the TCW movie.

Of did he? My mistake, I guess the RotS novel is now even MORE non-canon.

Not really. There's some time between Dark Rendezvous, LOE, ROTS and Witches of the Mist. Plenty of time for Dooku to be thoroughly cowed by Sidious.

No. Non-canon.

Even if Sidious can resist (which there is no proof to demonstrate that Nihilus drain is the same as force drain which anyone can use), how long can he resist? Nihilus can just instantly and constantly drain Sidious, no matter how much sidious resist it is going to heavily tax him to defend himself constantly at all times.

Nihilus could also be using his unrivaled TK against Sidious to either kill him, or keep him at bay until his drain pierces his defenses (that is if sidious can even resist).

I notice quite a few people keep saying Sidious lightning or speed will win him the match, yet Nihilus is also going to have force speed so the difference between the two wont be big. Furthermore Coulnd't Nihilus just drain and consume the force lightning since it is made out of the force, and that is what Nihilus "Eats"?

Sidious in all 3

Originally posted by The_Tempest
All the Emperor needs to trigger a Force storm is "mere thought and inclination" (The Essential Guide to the Force).

More importantly, between Dooku's excavation of the Dark Reaper and Palpatine's own prodigious demonstrations of a Force drain, it's silly to think he's incapable of wielding it against a single opponent.

I think it comes down to who's quicker on the draw and it can be reasonably inferred that Palpatine's arsenal is much wider than Nihilus's. At worst, I think it's a stalemate.

One cannot actually drain a wound. Nihilus tried that on Meetra.

Originally posted by Dolos
One cannot actually drain a wound. Nihilus tried that on Meetra.

A "Wound of the Force". It's so stupid. In that way, Sidious is a "Black Hole of the Force", Dooku is "Centrum of the Universe", Mace is "Superconducting Loop" and Yoda is "Fountain of the Light". Yuppi!

Well, as Nyrriss showed, force lightning and lighstaber in hand is enough against that "wound".

Theres nothing stupid about the concept and that isn't a comparison. Those are simply metaphors, whereas Meetra's status as a Force Wound is an actual attribute she possesses and is the basis for her various abilities. Those are descriptions, hers something that actually affects herself and those around her, like Cognus' ability to weaken Force users.

Yoda doesn't have special "Fountain" powers!

Originally posted by Nephthys
Theres nothing stupid about the concept

umad Temp?

What is so stupid about it? The Force is a universal energy field. It can be tainted by the darkside in places, it only stands to reason that likewise there can be places where it can be tainted to the point of becoming "wounded". All life in the galaxy is interconnected and pain and death is transmited through it and so when a significant number of lives are lost, it makes sense for the Force to sustain a localized injury much like someone who who had lost a limb. "Absenses" in the Force also make sense based on the way the Force works.

Furthermore the concept that mass death and war damages the Force is one thats thematically strong and compelling imo. Life breathes the Force, makes it grow. That death would affect it strongly showcases just how damaging these conflicts are.

Infamous Accolades
"The extent of his power cannot be put into words… and his perceptions have grown as well. To him…"
"You are dust motes in a storm… a grain upon the beach… and as insignificant as a body that orbits the graveyard of Malachor."
-Tobin and Visas Marr, regarding Nihilus (Knights of the Old Republic 2: The Sith Lords)

"My people never saw his face when he struck—but they heard his voice. When my lord spoke, every living thing on Katarr died. The destruction of Katarr echoed through the Force, the screaming of countless lives."
-Visas Marr (Knights of the Old Republic 2: The Sith Lords)

"He is a wound in the Force, more presence than flesh, and in his wake life dies… sacrificing itself to his hunger."
-Visas Marr (Knights of the Old Republic 2: The Sith Lords)

"There is no strength in the hunger he possesses… and the will behind his power is a primal thing. And it devours him as he devours others—his mere presence kills all around him, slowly, feeding him. He is already dead, it is simply a question of how many he kills before he falls."
-Kreia (Knights of the Old Republic 2: The Sith Lords)

"This ship… is it his weakness? It should not exist, yet it cruises the darkness between the stars. He tore it from the mass shadows of Malachor, along with his fleet… that is a measure of his power."
"The structural damage should have destroyed it long ago"
"...He holds it together."
-Colonel Tobin and Canederous (Knights of the Old Republic 2: The Sith Lords)

"You… you are the darkness in which all life dies, milord. All life… exists to feed your power, and my life… my life is yours. I beg you… please… let me die. […] Yes… this disturbance… echoes through the Force. I can follow it to its source… and bring it to you. I will leave at once, my lord."
-Visas Marr to Nihilus (Knights of the Old Republic 2: The Sith Lords)

"He cares nothing for the Sith or its teachings… or the Jedi. And when the Jedi are dead, he will feed on the galaxy, the Republic, and eventually, consume the Sith as well."
-Kreia (Knights of the Old Republic 2: The Sith Lords)

"Darth Nihilus, the Lord of Hunger, is a survivor of the Mandalorian Wars. His appetite for power consumes entire worlds."
-Star Wars: The Ultimate Visual Guide (Page 29)

Notable Feats/Accomplishments:
-Can destroy whole planets by sucking away all force/life. (Force Drain)
-Can sense almost anything and everything in the entire universe, although he only pays attention to the things that serve his hunger. (Force Sense)
-Can lift a whole fleet of star ships off of a planet into space; and keep them together when they should be damaged beyond repair. (Telekinesis)
-Can make slaves out of anyone just by speaking. (Force Corrupt)
-Striped Traya of the Force. (Sever Force)
-Able to keep his Force powers functioning even as far as an entire Star System.
-Dueled on pair with two Jedi (Meetra Surik and Visa Marr), as with Mandalore.
-Defeated Darth Sion and Darth Traya
-Essence Transfer to the point where he was merely a spirit in a cloak and his spirit was able to be contained 5000 years after his death.

More Powers and Abilites:
-Force Scream
-Force Lightning
-Force Whirlwind
-Force Resistance
-Dark Rage
-Dark Healing
-Farsight
-Tame Beasts

Important Links:
http://www.youtube.com/watch?v=KHSstYl9Yfs (The full comic which illustrators the destruction of Katarr)
http://www.youtube.com/watch?v=2qyGRYEihqo (The final fight nearing the end of KOTOR2)