Questioner
Eithan vs. Hellsing: I think Hellsing would lose, but how would the fight go?
Eithan vs. Queen Mab from the Dresden Files
Eithan vs. Thor
Yerin vs. the Juggernaut (from x-men)
Lindon vs. the Wolverine
**POSSIBLE SPOILERS FOR BLACKFLAME**
Eithan vs. the turtle in Blackflame: We know already that the turtle will win the awesomeness fight, but in a death match, which would walk out? (The turtle was mentioned in the previous blog)
Will Wight
1.) Eithan vs. Alucard
I'm assuming you mean Alucard as an individual and not the Hellsing Organization as a whole. Eithan would win because, as overwhelming as Alucard looks, he has a number of exploitable weaknesses.
One-on-one, Eithan would just keep cutting him up until he fully released his powers or ran out of regeneration. If he fully released his powers, then his original body is vulnerable, and since Eithan can instantly sense everything around him in a fairly broad space, he would know that and kill the original.
Even in the situation where he had to go around killing all the individuals, an army isn't really much threat to an Underlord.
2.) Eithan vs. Queen Mab
I...am going to skip over this one for spoiler reasons.
There's a subplot in Blackflame that revolves around what Path Eithan is on, and I can't answer this question without affecting your interpretation of the Path.
3.) Eithan vs. Thor
If you mean the Marvel comics Thor, that would be a good fight. Thor can fly and summon lightning, which would be difficult to deal with, but in the end if Eithan was really motivated to kill him, he could.
No specifics, again, because I don't want to influence your reading of Eithan's Path.
4.) Yerin vs. the Juggernaut
I'm not sure...this is a cool matchup to consider. I'm playing this fight out in my head, and I think it would come down to how long it took Yerin to figure out that she needed to get his helmet off.
She couldn't break the armor, but at the same time he'd be too slow to hit her. I'd think she'd probably kill him through gaps in the armor, cutting him slowly with sword madra. Death by a thousand cuts.
5.) Lindon vs. Wolverine
Wolverine tears him apart. No contest.
Now, if you mean Lindon versus A wolverine, I think he could probably handle that.
6.) SPOILER ALERT
Eithan vs. The Turtle
NONE CAN STAND AGAINST THE MIGHT OF THE TURTLE!
(...but not really, Eithan would win.)