The X-Men’s Dark Phoenix vs. the Watchmen’s Dr. Manhattan? Neither requires corporeal form… Dr. Manhattan, apparently, can create human life. Dark Phoenix can live in the sun. Who wins? Can there be a winner? For the sake of this deathmatch, let’s say there must be a winner.
“There can be only one…”
I’ll say Dr. Manhattan, because his power has been shown to encompass both destruction and creation, and his control goes to a much finer level.
Naked Blue dude vs. Hot Chick. Tough call.
Maybe it is a matter of perspective. I had problems finding a picture of him that he is not rated R. 
(needs small red spot)
You mean this?
It’s just a bunch of squiggly lines.
Dr Manhattan sees all time lines past present and future at the same time. Also he can build and destroy things at the atomic level. he could live in the sun. He could also turn the sun into a giant 16 million mile wide turkey wearing a lei and a top hat if he so choose. He could make dogs and cats live together in harmony. He could take the form of the Stay Puff Marshmallow man. He could beat Superman without a thought. Essentially he is God incarnate.
Doctor Manhattan’s level of power could only be matched in the Marvel universe by such thing as the Celestials, the Beyonder or the Infinity Gauntlet. So if the these two beings of phenomenal cosmic power did cross paths they might have a brief battle which would completely depend on Doc Manhattan’s mood at the time, so I am going to vote for Phoenix because I can.
Quoting from the Wikipedia entry on the Phoenix:
The Phoenix Force is an immortal and mutable manifestation of the prime universal force of life and passion. Born of the void between states of being, the Phoenix Force is a child of the universe. It is the nexus of all psionic energy which does, has, and ever will exist in all realities of the omniverse, the Guardian of Creation, and a de-facto guardian of the M’Kraan Crystal.
The Phoenix is among the most feared beings in the entire existence — having the power to cut and re-grow any part of the universe, as well as destroy it entirely, which is part of the Phoenix’s purpose: “The Judgment of the Phoenix”, to burn away the obsolete. The Phoenix Force is described as being “the embodiment of the very passion of Creation – the spark that gave life to the Universe, the flame that will ultimately consume it.”
The Phoenix will become Dark Phoenix if it allows human emotions to cloud its judgment. In this state, Phoenix is the strongest, but also is an evil entity. It thirsts for power and destruction. Totally uncontrollable, it is a force to be reckoned with as it is not bound by a human conscience. When Dark Phoenix flew back into space, her true firebird form was seen across the entire universe and even demanded the attention of Eternity.
The Phoenix Force has the ability to manipulate cosmic energies and to tap into the life-force reserved for future generations, thus denying them existence. It can wield this energy to project beams of immense destructive force. It can transmigrate throughout time and space by folding its energy back into itself, causing it to collapse akin to a black hole and then reform itself upon reaching its destination. It can directly absorb energy such as Cyclops’ optic blasts or even the entire energy of a sun. It is also capable of absorbing the energy and life-force from a foe. As it is the nexus of all psionic energy, it has mental abilities of cosmic scope, including telepathy and telekinesis.
Dark Phoenix probably wouldn’t even take notice of Dr. Manhattan as she (it?) wiped him out of existence.
Rough one really both seem to be on the cusp all powerfulness. but i call phoenix cause Dr Manhattan doesn’t seems to care to much about other life. phoenix seems to want to exterminate it all. She has passion and passion tends to win over lethargy.
He is believable as a second god. I suppose within the Watchmen universe he would be the first god, since the work is so nihilistic. Something about his disinterest in exploring what it means for a human to become god turned me off of him as a character, but I’ve got to admit he’s a powerhouse.
I am going with Phoenix, too, for this exact reason.
Doctor Manhattan sees himself as a cog in the wheel of the universe, whereas the Phoenix is a literal force of nature, pure passion, pure power. In a very real sense, they represent the polar opposites of order and chaos. For all of his power, DM believes that his every action is predetermined and part of the integral design of existence. The Phoenix Force, OTOH, is rage and lust and love and hate, all on a cosmic scale. Such passions, especially when driven by human imagination and whims, are inherently unpredictable, even to one such as Manhattan. Considering how things were concealed from him in the storyline of Watchmen (being purposely vague here), he has limits. Phoenix does not.
If 1) Phoenix can time travel and 2) since she’s clearly not afraid to interfere with human affairs – unlike Dr. Manhattan – then she could have an edge over Dr. Manhattan, who just sits back and watches things unfold. Assuming that Wikipedia entry is correct, Phoenix may have a theoretical edge, then.
Hmmm…sounds strangely familiar. Vorlans v. Shadows, perhaps?
And look how well that worked out. 
Who are you? What do you want? What is your favorite color? 
Green…no, blue. Aaaaaaahhhhhh!