Thor isn't going to do anything different with a day of prep - Doom on the other hand is capable of nearly anything with prep.
Doom 8/10
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Of what consequence are you now? These people, this world, they are nothing - the universe is power, pure unstoppable power - and I am that force, I am that power.
Doom. Simply because Thor only has a couple decent methods of attacking. If Doom keeps his distance and uses his ranged attacks sparingly Thor is left guessing and needs move in, in which Doom can use his surprisingly decent H2H. A nice fight, but I'm sticking with Doom. Although, Thor could land a couple of nice hits, but nothing to beat down Doom or make him change tactics. Thor isn't a bad fighter, it's just that Doom has a whole load of tricks up his sl-....cloak.
I'm surprised to see everyone going for Dr. Doom right now (though I am sure some will be fighting for Thor soon), but I have to agree.
I didn't post my opinion in first post because I don't like to see see a thread lean a certain way because of the original poster.
Though I think Dr. Doom would win. With a day of preparation, he wouldn't be able to do MUCH but he would have ample time to analyze Thor and come up with a plan. Thor doesn't have a weakness (except being separated by his hammer) so he can't come up with an invention of some sorts to deplete him on his energies.
Though I think with Dr. Doom's synthesis of magic, science, and intelligence will help him prevail, though it won't be easy. Thor has fought foes of incredible strength, varying of many different powers. Thor is actually very familiar with magic facing off against his brother on many many occasions. Thor has even faced off against Dr. Doom before (though not sure if he was alone ever, and if he was, it was a very long time ago and Doom has become more advanced).
How often does Doom come up with über weapons that can take out high heralds in a single day? Because his recent plans and plots haven't exactly put him on par with the high herald guys.
Couldn't Thor just ask his dad? or contact some of the other skyfathers?
Didn't Thor one-shot almost one-shot Annihilus? Or at least take the explosion that knocked out Annihilus?
I just don't think that being able to understand and use outside sources means that you're capable of instantly coming up with insane devices that let you instantly beat anyone far up in the Herald tier.
I can't remember the issue number off the top of my head, but I seem to remember Doom tripling the power of his standard armor with something like 20 minutes worth of prep during the Acts of Vengence storyline.