When it comes to pure, raw, unadulterated power there are few people that come even close to the doctor. In fact, there is almost no defined limit to what he can do. The reason he is at #20 however, is due to his primary weakness (besides tachyons) – apathy. In spite of being able to annihilate essentially the entire universe he just doesn’t care enough about much of anything and would prefer to be left alone.
As one of the most powerful telepaths in the universe, Jean Grey sometimes has trouble keeping her nearly unlimited mental powers in check. Professor X was even forced to construct psychic shields in her mind as a child in order to prevent her from fully realizing her power until she was mature enough to handle it on her own.
Essentially a combination of Superman and the Silver Surfer, Captain Atom is sometimes seen as a second rate man-of-steel. His powers are formidable, however, with the ability to manipulate theoretically unlimited amounts of energy.
Although Wolverine doesn’t have any of the typical superhero powers, it’s the intangibles that put him on the list. What he lacks in raw power he makes up for with pure fury. And as we’ve seen with Dr. Manhattan, attitude is half the battle.
As one of the most powerful superheroes in the Wildstorm universe, Mister Majestic bears a deliberate resemblance to Superman. With essentially all of his powers we just couldn’t rank a copy above the man himself.