I'm going to take someone else words on why Bellamy sucks that arc especially:
Loathe: If Mr 2 and Mr 3 are examples of re-introducing a character with success, Bellamy is the exact opposite. To put it bluntly, Bellamy in Dressrosa plain doesn't work, and it feels like he was reeled in simply because he had a connection with Doflamingo in a previous arc. His role could've worked if about 5 of the other Dressrosa plotlines had been axed, but as is, Bellamys subplot is possibly the most clear example of the arcs haphazard nature, like with the ”kill Luffy!" plotpoint that goes nowhere, because Dellinger stops Bellamy just before he's about to go kill Luffy. It reached a point where ”pulling a Bellamy" is now a thing people fear- that is, a character vanishing for a huge chunk of the story, yet us being expected to care when they reappear at the last minute. For instance, the current arc has mostly dodged this by keeping the spotlight on Capone/Caesar/Jinbe once they popped back up, but I'd say Pound is currently pulling a Bellamy.
Anyway, Bellamys role in Dressrosa is built on his relationship with two people, Luffy and Doflamingo, and neither fully works.
With Luffy, even though its been two years (and even longer IRL), his instant-friendship with Bellamy feels jarring. With Mr 3 we got to see his character growth firsthand, but with Bellamy we're just to accept that he's now a better man, and now Luffys friend (despite the bizarre comment about Skypeans when they first met). Luffy may be the type to forgive and make friends easily, but, like with Fukaboshi, just saying that the characters are friends doesn't mean the readers are invested. If Luffy and Bellamy had gradually come around to respecting each other instead of instantly, it'd have been more compelling.
Then, Doflamingo. Now theres no problem with depicting abusive relationships in fiction, and that's absolutely what this is. But when every single interaction between Doffy and Bellamy involves the latter getting fucked over and left for dead, you need a good reason for Bellamys continued admiration. And the micro-flashback of ”Wowie its Doflamingo! I'm a big fan, can I join you?" ”Whatever" is not enough. In the context of Jaya you don't need anything except ”Bellamy is a Doffy fan, Doffy doesn't give a shit oh snap", but when you make it an emotional centerpiece of an arc, you need more. Why does Bellamy think Doffy in particular is so great? We don't know. Again, something good could've come of this by contrasting him to Bartolomeo or Law, or playing up that he doesn't understand Doffys true World Destroying desires, but this never happens.
So in the end, when Luffy fights Bellamy, we don't really buy the supposed friendship, and we don't buy Bellamys unquestioning devotion, and Bellamy comes across as the worlds biggest, dumbest cockhead. At this point he knows Doflamingo is terrible and does not, and will not, ever care about Bellamy – and yet he still obstructs the efforts to stop the genocidal maniac! Because ”"pride"". That's not a fucking valid reason! Theres nothing admirable about Pride in and of itself! Its having Pride in your Pride! Like, If you found out the leaders you admired were literal sadistic Nazis, and you kept fighting for them anyway for no other reason than ”it would not be honorable to leave just because they turned out to be monsters", then guess what, you're a complete moron. I guess you can make the case that Bellamy is supposed to come across as pathetic, but then you also have that line from Luffy about "being a man", so ehh.
The message Bellamy conveyed in Jaya was "chase your dreams, and those who doubt you aren't worth your time."
In Dressrosa, I guess we're supposed to find his "dream" of pig-headed loyalty to his abuser somehow admirable and/or sympathetic? Screw that.
Mostly because in the end, as was said, theres no closure for Bellamy. Then again, even Laws reaction to Doflamingos defeat was muted, but it still makes everything feel rather pointless.
Editor comment:
Editor Naito's comment about volume 85:
"This volume is full of amazing highlight scenes which I consider would go down in ONE PIECE history. Highly recommended for Sanji fans!! "