It was doom from a possible future that got tortured by Odin.
I say possible because I know marvels wacky "change the past, create a new timeline" wackyness.
Actually IIRC, if you used the DLC Doom he would always acknowledge the one you fight as an impostor. If that is canon, then the 'Doom' being tortured isn't the real Dr. Doom.
Although that would raise attention when Thor brings up that he took down Dr. Doom with the aid of Dr. Doom in his stories...
I don't consider the DLC characters to be canon regardless. Cyclops and Colossus were supposed to be captured and altered in the end, and Nightcrawler was supposed to be either in captivity, dead, or regaining his strength throughout the game. And I don't see the villains and heroes working together at all.
The world is cruel. And the only morality in a cruel world...is chance. Unbiased. Unprejudiced. Fair.
I see doom as marvels greatest hero. Some of the dlc chars make no sense but doom does. I only mention the future doom in the way I do because marvel has a wacky rule about time travel not actually affecting the past but creating an alternate timeline.
EDIT: I don't think the dlc has to make sense either way. These games are more about people being able to whip ass w a friend(s) playing as thier favorite superheroes.
"there are only two reasons to date a girl you already dated: breast implants" ~ Barney Stinson