I signed up not even ten minutes ago so let's make haste with my first contribution.
Alucard. For all his crazy forms and powers they have not resulted in anything other that physical endurance and physical damage. In other words he has very direct and indirect ways to cause damage. His regeneration is also some of the best I have ever seen (key word is 'I' as I have not seen all regenerators under the sun). His biggest issue is that I've never seen him approach any fight in a serious fashion.
His speed comes into question. I don't recall him ever moving all that fast. However, I do remember that Alucard fought against a synthetic vampire that was exceptionally fast. I have nothing beyond source>derivative logic to back this up but I find it hard to believe that synthetic vampires created from Alucard's essence are faster than him.
The question is is Alucard as fast or faster than Uliquorra?
Uliquorra. His abilities are straight forward: strength, endurance, energy projection, speed, and regeneration. Although he is not 100% exempt from it he is fairly free from Plot Induced Stupidity relative to his shonen counterparts.
His strength is debatable but I don't remember anyone from Hellsing being strong enough to casually throw someone who can resist with flight down several city blocks (ripping through pavement nonetheless). Of course I'm talking about a strength feat executed by Grimmjow when he first encountered Ichigo but Uliquorra and Grimmjow's physical strength are at the very least comparable.
So in a final analysis....
In a straight up fight Uliquorra could literally Sonido circles around Alucard all the while Cero'ing the living F*** out of him. This would be the first fight that Alucard would have to take 100% seriously and based solely on that aspect, we can see Alucard perform feats that were previously unknown or thought to be unreachable.
Still, I like this match up and kudos to the OP for selecting it for discussion.