I agree with your OP in how Magolor's chances are severely underestimated by the majority of the community, I feel that while Bandana Dee does edge him out, Magolor has quite a few qualities that nearly even it out, I think he's a lot closer to BDee chance-wise than most people think he is. I wouldn't say he's top 5 though, I'd probably put him around number 7 or 8 personally, but that's just me.
Also, bit off topic, but I kind of wish the Kirby fanbase just banded together and picked one character or a unitary concept like literally voting for "Kirby rep" in the ballot instead of bickering over who we get and just make it clear how badly we wanted more representation, we'd be practically unstoppable in terms of sheer numbers if that happened. I mean, from what I've seen (I could be wrong) most Kirby fans would accept nearly any new character from Kirby, and while we all have our preferences over who we want, I think it would have been good for us all if we did that. But that's in the past, the ballot's over, so there's nothing that could be done about that this game
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Now for a question, if Magolor were to get in, would you rather he have a voice or no voice? I'd personally want him to make non-legible weird squeaky/gibberish noises like the ones he makes when you talk to him in KRTDL.