As an apology for my low content post, I will now write character impressions about the only guy I know: Dedede!
So everyone seems to agree dedede has polarised match ups, and based on my experience in for glory and reading posts here, most people would say the polarisation occurs on the axis of zoning power. The more zoning a character is, the worse for dedede, and zero projectiles means dedede wins! As a result, I see a lots of characters counter picked that have many zoning options: DHD, Villager, Links, Samus etc. if this all makes sense to you then you are in good company, but I disagree with it.
My only experience is thousands for glory so take my stuff with a pinch of salt, better players than me have stressed the difference playing offline makes. With that out they way, my opinion is that once you have any projectile at all, the most important thing is how mobile you are, how safe your attacks are, and how well you can recover.
Compare yoshi, sheik and fox to DHD, villager, and toon link for example. Now, the first set may just be outright better but I also believe they are more troubling to dedede in particular. Eggs, needles and blaster are already enough to force dedede to approach. The wall of projectiles the latter set of characters offers is really just overkill. The difference is, when you get in on the zoners, life is pretty good. When you get in on sheik or fox or yoshi you're in on... Sheik and fox and yoshi. These characters are also good at avoiding gimps or have varied options to recover that makes it hard for dedede to do what he does best: edge guarding!
Some of you might be objecting at this point. "Sure, DHD has vulnerable recovery but villager's recovery is insane!" That's true for most characters, but honestly villagers comfort off stage isn't enough to prevent dedede bullying his relatively vulnerable up b. The rules of what's safe or not change quite a bit with dedede.
So yeah, right now I love fighting the heavy zoner characters. The match ups are hard at neutral but equally brutal for them during my advantage time. The top tiers with projectiles though? They scare me. I'm forced to approach, but I'm also not ever at as big an advantage. This isn't just a power level difference thing either, imo. If Rosalina is still top tier, she's relatively fine for dedede. I don't know if dedede has the advantage, but he can abuse her recovery, has a very easy time killing luma, and isn't under heavy pressure at range. Lovely.
I hope I've paid off my off topic sins, thanks.