Sora
He ABUSED THE POWER OF WAKING 8 FLIPPIN' TIMES. It's a NATURE TABOO! He got away with it too, I wish he'd get some comeuppance and just disappe-
oh.
OH NO.
Ummm... I mean Tarzan's whole world!
Seriously though I'm having a hard time choosing. Ask me years ago and I would have said Axel in a heartbeat because I never really liked him. For the me right now to erase someone they would have to fit in one of these categories:
Be completely inconsequential to the story's progression.
Undermine the story.
Lead to unnecessary problems IRL.
Lets start out with characters I have no reason to erase:
Riku: TBH Riku finished his character arc in 3D, which is why he's so flat in KH3. His previous arcs (feeling jealous of Sora, caged in on his world and his regret and shame for to falling into darkness) were dealt with, but he didn't have an arc to replace it with in that game. His motivation in KH3 was basically "I'm a good guy so I'll do good things," which is nice and all but boring character-wise. Hopefully his motivation to save his best friend will give him an interesting arc to grow with again.
Kairi: She gets a lot of hate on here for being a damsel in distress and my reaction to that is: "Who cares?" Damsels in distress are so prominent because they are good motivations for stories. Even if you don't like the idea of it, that doesn't mean they don't have a place in stories nor that they shouldn't exist. She had a role to play, and I say she played it well. That doesn't mean that she can't do anything else either and she has a real motivation in trying to retrieve Sora from the land of the dead.
Now you might notice that I talk about motivations up there. Characters need motivations or else they have no real reason to even participate in the story. Which is why in the coming arc Roxas, Xion, and Namine feel like they don't belong.
Roxas: As a character he lost all of his motivations, being wanting to be himself and with his friends which, y'know already happened. I would have preferred him dying for good in KH2 but, eh. I mean he could take the road of looking for Sora too, but it seems a bit odd because besides being the same person, there was never any deep interaction between the two. It would just come off as an impersonal goal, even though they were literally the same person before. Weird how that works.
Xion: Even though she was also a part of Sora she isn't close to him at all, so she shares a lot of similarities with Roxas here. She also has absolutely no motivation either, and I'd say that her progression was done in 358. She doesn't really have any goals as a character right now much like Roxas. They are in the exact same boat.
Namine: She's a bit different. It's less of a problem of motivation. She's close personally with Sora as well as being- wait a minute. I just realized, Sora barely knew her at the end of KH3, why'd he seem so tight with her? She knows him well enough, but he only knows her as the girl in Kairi. I'm sorry, I totally lost my train of thought in this one because of that epiphany.
Um... Well. Axel and Isa, Maluxia and Larxene, and Terra, Ventus, and Aqua are all exempt from that section. Axel and Isa have the motivation of Subject X even if I don't think Axel is that close to Sora, he will probably be more involved when that plotline comes in. Marluxia, Larxene and Luxord and Demyx are all currently plot relevant from the X side and possibly moving forward, with the former two's motivations being unclear, but developments seem to be on their way. The Wayfinders signed up for the job of being Keyblade Warriors and to keep chaos from running about, and MoM/Whoever will be the next villain seems to have a connection to the past/Ven and that could be a reason for all three of them to form up in solidarity. One motivation three people.
Hmm... I guess I'd erase... Anyone who got in the way of Setzer, Fuu, and Rai? Their the greatest after all, Y'know?