Two of my favorite villains in comics, and the respective villains of their universes (Actually, maybe Darkseid beats him there.). Who takes this one? Ra's has been around for centuries and he has an entire League Of Assassins at his disposal. He's also an expert in Swordfighting. BUT, Doom has his armor and all of his technology as WELL AS all of his arcane knowledge at his disposal. This can certainly end in a stalemate, but if one had to win, I would say Ra's because he's impossible to kill (And he actually HAS been killed a few times.).