@Monkey:
Well he confirmed…
-Symbolic comparisons between them
-Shanks as a future probably doomed adversary to him
-Has been building him up more than anyone in the series not part of the main cast (unlike Akainu or lol Kong)
-Has made him a D, the only evil one thus far
The arguments for Blackbeard as last boos are many, deep, and strong.
The Marines are extremely poor candidates given that they already have adversaries being built up....the other Marines. Has not a Marine internal conflict been clear since pretty much the start of the series? You yourself see Smoker and Coby as being good guy Marine higher ups by the end right? Well who do you think their main enemies are in reality?
I noticed what you said long ago, and I trully wanted that Blackbeard was the final boss if the marines didn't exist and the One Piece wasn't about the lost century. but as much as I want, I can't wrap my mind that Blackbeard is a worth oponent for one glorious final, he can't compete against a giant organization even if he has one an ancient weapon.
Whitebeard trully said that a great war against the marines will come once One Piece is found. This war that will envolve the entirely world will be followed by a mere fight against a bunch of pirates? No way, this is anticlimactic.
You could think of Blackbeard as the last boss for the title of the King of Pirates, after Luffy defeating the other yonkous. And then Luffy will call all pirates against marines.
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@Strawhat:
Not to mention Blackbeard is the one that threatens the world, not the World Government or the Marines. The WG is just a shade-grey, conservative organization trying to keep the status quo. Not exactly a great final-boss material.
You don't know what they'll find with One Piece.
And they already threated the world in the war against the lost kingdom.